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Newsela | Understanding tropical deforestation

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Deforestation meets some human needs, but also has profound consequences that aren't just local, but global.

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Thriving shrubs also crowd out lichen, an important food source for caribou and other animals. Warmer tundras could also see increased risk of wildfires and drought-scientists have documented a significant disappearance of lakes in western Greenland between 1969 and 2017.

Air pollution. Air pollution affects tundra environments in different ways. A recent study found that Arctic clouds are particularly sensitive to air pollution, which spurs cloud formation and has a blanketing effect. Black carbon from diesel engines, fires, and other combustion can settle on snow, decreasing its ability to reflect sunlight and causing faster melting.

Chemicals used in coolants and aerosol sprays have driven ozone depletion at the North and South Poles, which can let in stronger ultraviolet rays. And toxic mercury, sent into the atmosphere by coal-burning and industrial activity, is accumulating in the Arctic tundra, threatening both humans and animals who live in the region. Air pollution can also harm or kill the important food source of lichen.

Industrial activity. The oil, gas, and mining industries can disrupt fragile tundra habitats. Drilling wells can thaw permafrost, while heavy vehicles and pipeline construction can damage soil and prevent vegetation from returning. This activity also increases the risk of toxic spills. Seismic testing for oil and gas operations in the 1980s left tracks on the tundra that are still visible decades later.

Invasive and migrating species. Climate change is driving down populations of some Arctic tundra natives such as caribou (also known as reindeer) by fostering an increase in parasites and disease while damaging food sources. But other species, such as shrubs and the wolf spider, are thriving.

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Climate-driven changes in these harsh lands at the ends of the Earth could have a worldwide impact.

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Spi images for Biodiversity Asset Library topic collection

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Science for Kids: Tropical Rainforest Biome

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Kids learn about the tropical rainforest biome. This diverse ecosystem produces much of the Earth's biodiversity.

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The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125 to 660 cm.) of rain falls yearly.

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Kids learn about the desert biome. The dryest areas on Earth still have plant and animal life.

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Science for Kids: Savanna Grasslands Biome

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Kids learn about the savanna grasslands biome. This tropical ecosystem is full of large herbivores like zebras, giraffes, and wildebeests.

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Kids learn about the taiga forest biome. The largest of the land biomes is known for its evergreen trees.

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Midwest battles to keep invasive Asian carp out of the Great Lakes

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Seagrass Meadows - Oceans (U.S. National Park Service)

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A healthy watershed means healthy seagrass. Seagrasses need clean water and sunlight to thrive. Nitrogen and phosphorous from sewage treatment plants, streets and farms can pollute coastal waters and cause blooms of algae that deprive seagrasses of light and clean water. Dredging and shoreline development also damage seagrass habitat.

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Mangroves - Oceans (U.S. National Park Service)

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Despite their many benefits to our coasts, mangrove habitats are under threat worldwide. Many mangrove forests have been converted to commercial fish and shrimp farms. In the U.S., parks protect some of our mangrove forests from development but they are still vulnerable to pollution and sea level rise.

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How are coral reefs formed?

Corals reefs are formed over a process of thousands of years. Each coral reef is made up of colonies of tiny animals called polyps. Each polyp produces calcium carbonate, which makes up their skeleton and protects corals internal bodies; similar to how our skeleton protects our organs. Polyps on their own are colorless, however, each polyp attracts large amounts of algae, called zooxanthellae. These algae live inside the cells of the polyp and gives corals their vibrant colors.

Corals, and the algae inside their polyps, rely on sunlight to produce the energy needed for them to survive and grow. That's why most coral reefs can be found in shallow, clear water along the coast. Corals crave the marine conditions found in the warm waters of the tropics and sub-tropics.

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Coral Reefs - Oceans, Coasts & Seashores (U.S. National Park Service)

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Corals reefs are formed over a process of thousands of years. Each coral reef is made up of colonies of tiny animals called polyps. Each polyp produces calcium carbonate, which makes up their skeleton and protects corals internal bodies; similar to how our skeleton protects our organs.

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The Florida Department of Environmental Protection is the state's lead agency for environmental management and stewardship - protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida's natural resources and enhance its ecosystems.

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Florida is the only state in the continental United States with extensive shallow coral reef formations near its coasts. Coral reefs create specialized habitats that provide shelter, food, and breeding sites for numerous plants and animals. This includes ones important to fishing like spiny lobster, snapper, and grouper.

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The Florida Department of Environmental Protection is the state's lead agency for environmental management and stewardship - protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida's natural resources and enhance its ecosystems.

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Mangroves are one of Florida's true natives. They thrive in salty environments because they can obtain freshwater from saltwater. Some secrete excess salt through their leaves, while others block absorption of salt at their roots.Florida's estimated 469,000 acres of mangrove forests contribute to the overall health of the state's southern coastal zone.

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The Florida Department of Environmental Protection is the state's lead agency for environmental management and stewardship - protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida's natural resources and enhance its ecosystems.

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St. Martins Marsh Aquatic Preserve - DEP Staff - Jamie Letendre - Sea turtle.jpg Seagrasses are grass-like flowering plants that live completely submerged in marine and estuarine waters.

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The Florida Department of Environmental Protection is the state's lead agency for environmental management and stewardship - protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida's natural resources and enhance its ecosystems.

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Salt marshes are coastal wetlands rich in marine life. They are sometimes called tidal marshes, because they occur in the zone between low and high tides. Salt marsh plants cannot grow where waves are strong, but they thrive along low-energy coasts. They also occur in areas called estuaries, where freshwater from the land mixes with sea water.

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Kids learn about the grasslands biome. Flat with few trees, these ecosystems feed much of the world.

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national oceanic and atmospheric administration

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Florida Keys National Marine Sanctuary protects the third largest living coral barrier reef system in the world.

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national oceanic and atmospheric administration

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Seagrass are flowering plants that grow entirely underwater

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Kids learn about the coral reef biome. Much of ocean life lives in this important aquatic ecosystem.

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The ocean is home to a phenomenal diversity of marine organisms. They have evolved to inhabit warm waters near the equator and the icy waters of the Earth's poles. Marine life takes advantage of the enormous volume the ocean comprises: from living near the sunny surface, to living in the dark deep sea. From humpback whales that travel thousands of miles in the open ocean to sessile rooted to one spot, marine life spans a fantastic variety of forms and plays a multitude of different ecological roles in Earth's global ocean system.

The nine animals on the fingertips in this photo were found near in the southern Caribbean, and represent a teeny-tiny fraction of life in the ocean. These gastropods and echinoderms were collected with a submersible below 60m (~200 ft) while Smithsonian scientists were searching for deep-sea crustaceans.

The photo makes me think about the diversity of life and whole communities not easily visible in the ocean and on land. Smithsonian researchers are attempting to document and monitor the biodiversity of coral reefs off Curaçao and hope to expand this deep-sea research to other parts of the Caribbean.

For some, the word "biodiversity" calls to mind tropical rainforests and coral reefs, while others think of the incredible variety of beetles or endangered species. Whatever the context, the word very successfully helps focus attention on the living components of the Earth's diversity.

Biodiversity is a complex concept, and it is helpful to think about it at different levels-ecosystems, species, and genes, to name a few. Ecologists, taxonomists, geneticists, and other biologists study biodiversity in different ways. Their collective work helps us better understand how species interact with one another and their environment, how they are classified, and how they evolve. These scientific findings show the value of protecting habitats, individual species, and the genetic diversity that gives rise to variation.

It is truly incredible to think about the species that have not yet been discovered. The Census of Marine Life estimates that there are at least one million species of plants and animals in the sea; most of which have not been described. When you consider that many of the known vertebrates are threatened with extinction, the call to understand the planet's variety of life becomes even more urgent.
Editor's Note: This is the sixth and final post in our "Summer in a Sub" blog series, which features the work of the Smithsonian's Deep Reef Observation Project (DROP).

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On Biodiversity: Understanding its Meaning and Importance

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The ocean is home to a phenomenal diversity of marine organisms. They have evolved to inhabit warm waters near the equator and the icy waters of the Earth's poles. Marine life takes advantage of the enormous volume the ocean comprises: from living near the sunny surface, to living in the dark deep sea.

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The deep-sea is a vast part of the world's ocean. Even today, it often surprises people to discover how much life lives in this largely unexplored and inaccessible world of darkness, cold and high pressure. In fact, it was once thought to be lifeless, before early explorers dredged the deep-sea bottom and pulled up creatures never before seen.

This summer, I joined the NOAA research vessel Okeanos Explorer, America's premier deep-sea exploration vessel, and had a unique opportunity to study habitats of the deep-sea. Among the most striking were deep-sea "coral forests."

Many of the corals we saw were octocorals, which aren't the "typical" warm water coral found in shallow waters that most people think of when they hear the word. These octocorals can form very large and very old colonies, some can be thousands of years old. Deep-sea octocoral colonies are only predators (unlike their shallow water relatives that often are also photosynthetic thanks to symbionts in their tissues). They feed on organic material as it flows past them on the water current and is caught by one of the eight feeding tentacles that surround each of the mouths of their many polyps.

Corals (and sponges) are what's been described as "ecosystem engineers"-their very presence provides habitat for many other animals, making them a habitat or "ecosystem" unto themselves. Several serpent stars, for example, live in close symbiosis with their octocoral host-so close in fact that they are almost never present as free-living individuals. Many of these stars spend their entire lives on the coral, with observations showing that some are present even as very tiny individuals. Museum specimens show us that many will not release from their host even after death. In the case of one species, this type of relationship can even protect the corals from human-induced threats-like an oil spill.

(NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana)

But, it's not just friendly relationships in an ecosystem, and octocorals have a very diverse and colorful "rogues gallery" of predators to deal with as well. Among them are a tiny jellyfish ( Aegina citrea) that settles on the feeding polyps present on the branch tips of some corals, devouring the tissue.

The worm-like mollusk called an aplacophoran can be found coiled around the stalks of corals after devouring the tissue on the stalk.

(NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana)

Prominent, often spiny goniasterid sea stars methodically feed on the soft tissues of the corals as they slowly climb up the body. Many of these predatory sea stars are known to remain on the corals for a very long period of time, with some observations suggesting that they have been present for over a year, making them more like parasites.

Giant sea spiders (or pycnogonids) are predators on multiple types of corals and will use their large proboscis to drain fluids out of the corals for food in a vampire-like fashion.

(NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana)

Although not strictly speaking a predator, a sea-anemone-like animal called a zoanthid overtakes the surface of some Paragorgia octocoral colonies, crowding over the original coral animal and competing with the coral's polyps for food.

We tend to think of an ecosystem as being large, like the deep waters off the Johnston Atoll that we explored. But even one single octocoral specimen can have its own collection of predators, prey and friends.

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Deep-sea octocorals: An ecosystem of their own

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The deep-sea is a vast part of the world's ocean. Even today, it often surprises people to discover how much life lives in this largely unexplored and inaccessible world of darkness, cold and high pressure. In fact, it was once thought to be lifeless, before early explorers dredged the deep-sea bottom and pulled up creatures never before seen.

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Smithsonian's National Museum of Natural History

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Mangroves, Biodiversity

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Are you a student researching corals or someone looking to learn more about coral reefs? This overview dives into everything to know.

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1. Home

2. Ocean Life

3. Plants & Algae

4. Seagrass and Seagrass Beds

Seagrasses are found in shallow salty and brackish waters in many parts of the world, from the tropics to the Arctic Circle. Seagrasses are so-named because most species have long green, grass-like leaves. They are often confused with seaweeds, but are actually more closely related to the flowering plants that you see on land. Seagrasses have roots, stems and leaves, and produce flowers and seeds. They evolved around 100 million years ago, and today there are approximately 72 different seagrass species that belong to four major groups. Seagrasses can form dense underwater meadows, some of which are large enough to be seen from space. Although they often receive little attention, they are one of the most productive ecosystems in the world. Seagrasses provide shelter and food to an incredibly diverse community of animals, from tiny invertebrates to large fish, crabs, turtles, marine mammals and birds. Seagrasses provide many important services to people as well, but many seagrasses meadows have been lost because of human activities. Work is ongoing around the world to restore these important ecosystems.

What Are Seagrasses?

A Plant, Not a Seaweed

Even though seagrasses and seaweeds look superficially similar, they are very different organisms. Seagrasses belong to a group of plants called monocotyledons that include grasses, lilies and palms. Like their relatives, seagrasses have leaves, roots and veins, and produce flowers and seeds. Chloroplasts in their tissues use the sun's energy to convert carbon dioxide and water into sugar and oxygen for growth through the process of photosynthesis. Veins transport nutrients and water throughout the plant, and have little air pockets called lacunae that help keep the leaves buoyant and exchange oxygen and carbon dioxide throughout the plant. Like other flowering plants, their roots can absorb nutrients. Unlike flowering plants on land, however, they lack stomata-the tiny pores on leaves that open and close to control water and gas exchange. Instead, they have a thin cuticle layer, which allows gasses and nutrients to diffuse directly into and out of the leaves from the water. The roots and rhizomes (thicker horizontal stems) of seagrasses extend into the sediment of the seafloor and are used to store and absorb nutrients, as well as anchor the plants. In contrast, seaweeds (algae) are much simpler organisms. They have no flowers or veins, and their holdfasts simply attach to the bottom and are generally not specialized to take in nutrients. Scientists are studying what genes were lost and which were regained as seagrasses evolved from algae in the sea to plants on land, and then transitioned back to the sea. The entire genome of one seagrass, the eelgrass Zostera marina, was sequenced in 2016, helping us understand how these plants adapted to life in the sea, how they may respond to climate warming, and the evolution of salt tolerance in crop plants.

Where are Seagrasses found?

Seagrasses grow in salty and brackish (semi-salty) waters around the world, typically along gently sloping, protected coastlines. Because they depend on light for photosynthesis, they are most commonly found in shallow depths where light levels are high. Many seagrass species live in depths of 3 to 9 feet (1 to 3 meters), but the deepest growing seagrass (Halophila decipiens) has been found at depths of 190 feet (58 meters). While most coastal regions are dominated by one or a few seagrass species, regions in the tropical waters of the Indian and western Pacific oceans have the highest seagrass diversity with as many as 14 species growing together. Antarctica is the only continent without seagrasses.

Growth & Reproduction

Seagrasses grow both vertically and horizontally-their blades reach upwards and their roots down and sideways-to capture sunlight and nutrients from the water and sediment. They spread by two methods: asexual clonal growth and sexual reproduction.

Asexual Clonal Growth: Similar to grasses on land, seagrass shoots are connected underground by a network of large root-like structures called rhizomes. The rhizomes can spread under the sediment and send up new shoots. When this happens, many stems within the same meadow can actually be part of the same plant and will have the same genetic code-which is why it is called clonal growth. In fact, the oldest known plant is a clone of the Mediterranean seagrass Posidonia oceanica, which may be up to 200,000 years old, dating back to the ice ages of the late Pleistocene. In some seagrass species, a meadow can develop from a single plant in less than a year, while in slow-growing species like Posidonia it can take hundreds of years.

Sexual Reproduction: Seagrasses reproduce sexually like terrestrial grasses, but pollination for seagrasses is completed with the help of water. Male seagrass flowers release pollen from structures called stamens into the water. Seagrasses produce the longest pollen grains on the planet (up to 5mm long compared to under 0.1mm for land plants typically), and this pollen often collects into stringy clumps. The clumps are moved by currents until they land on the pistil of a female flower and fertilization takes place. There is also evidence that small invertebrates, such as amphipods (tiny shrimp-like crustaceans) and polychaetes (marine worms), feed on the pollen of one seagrass (Thalassia testudinum), which could help to fertilize the flowers in a way similar to how insects pollinate flowers on land.

Self-pollination happens in some grass species, which can reduce genetic variation. Individual seagrass plants avoid this by producing only male or female flowers, or by producing the male and female flowers at different times. Just like land grasses, fertilized seagrass flowers develop seeds. Seagrass seeds are neutrally buoyant and can float many miles before they settle onto the soft seafloor and germinate to form a new plant. A few seagrass species such as the surfgrass Phylospadix can settle and live on rocky shores. Animals that eat seagrass seeds-including fish and turtles-may incidentally aid with their dispersal and germination if the seeds pass through their digestive tracks and remain viable.

Biodiversity

(From "Tropical Connections: South Florida's marine environment" (pg. 260), courtesy of the Integration and Application Network (ian.umces.edu), University of Maryland Center for Environmental Science. )

The 72 species of seagrasses are commonly divided into four main groups: Zosteraceae, Hydrocharitaceae, Posidoniaceae and Cymodoceaceae. Their common names, like eelgrass, turtle grass, tape grass, shoal grass, and spoon grass, reflect their many shapes and sizes and roles in marine ecosystems. Seagrasses range from species with long flat blades that look like ribbons to fern or paddle-shaped leaves, cylindrical or spaghetti blades, or branching shoots. The tallest seagrass species- Zostera caulescens -was found growing to 35 feet (7 meters) in Japan. Some seagrass species are quick growing while others grow much more slowly. These distinct structures and growth forms affect how seagrasses influence their environment and what species live in the habitats they create.

Ecosystem Benefits

Seagrasses are often called foundation plant species or ecosystem engineers because they modify their environments to create unique habitats. These modifications not only make coastal habitats more suitable for the seagrasses themselves, but also have important effects on other animals and provide ecological functions and a variety of services for humans.

Seagrasses have been used by humans for over 10,000 years. They've been used to fertilize fields, insulate houses, weave furniture, thatch roofs, make bandages, and fill mattresses and even car seats. But it's what they do in their native habitat that has the biggest benefits for humans and the ocean. Seagrasses support commercial fisheries and biodiversity, clean the surrounding water and help take carbon dioxide out of the atmosphere. Because of these benefits, seagrasses are believed to be the third most valuable ecosystem in the world (only preceded by estuaries and wetlands). One hectare of seagrass (about two football fields) is estimated to be worth over $19,000 per year, making them one of the most valuable ecosystems on the planet.

Key Services

Modification of the Physical Environment

(Richard Ling / www.rling.com)

Seagrasses are known as the "lungs of the sea" because one square meter of seagrass can generate 10 liters of oxygen every day through photosynthesis. Seagrass leaves also absorb nutrients and slow the flow of water, capturing sand, dirt and silt particles. Their roots trap and stabilize the sediment, which not only helps improve water clarity and quality, but also reduces erosion and buffers coastlines against storms. Seagrasses can further improve water quality by absorbing nutrients in runoff from the land. In nutrient poor regions, the seagrass plants themselves help nutrient cycling by taking up nutrients from the soil and releasing them into the water through their leaves, acting as a nutrient pump.

Creation of Living Habitat

Seagrasses are often called nursery habitats because the leafy underwater canopy they create provides shelter for small invertebrates (like crabs and shrimp and other types of crustaceans), small fish and juveniles of larger fish species. Many species of algae and microalgae (such as diatoms), bacteria and invertebrates grow as "epiphytes" directly on living seagrass leaves, much like lichens and Spanish moss grow on trees. Other invertebrates grow nestled between the blades or in the sediments-such as sponges, clams, polychaete worms and sea anemones. The accumulation of smaller organisms amongst and on the seagrass blades, as well as the seagrass itself, attracts bigger animals. As a result, seagrasses can be home to many types of fish, sharks, turtles, marine mammals (dugongs and manatees), mollusks (octopus, squid, cuttlefish, snails, bivalves), sponges, crustaceans (shrimp, crabs, copepods, isopods and amphipods) polychaete worms, sea urchins and sea anemones-and the list goes on.

Some of these organisms are permanent residents in seagrass meadows, while others are temporary visitors. A single acre of seagrass can support upwards of 40,000 fish and 50 million small invertebrates, and there are often tens to hundreds more animals in a seagrass bed compared to adjacent bare sandy areas. Hundreds of species live in the seagrass near the Smithsonian Marine Station at Fort Pierce in Florida. A number of the species that depend on seagrasses are important for commercial and recreational fisheries. In fact, in all regions of the world fishermen will specifically seek out seagrass beds for their abundance of fish. It is because of the wide variety of different species that live amongst the grasses that seagrass beds often form important "biodiversity hotspots." Not only do seagrasses support a diversity of marine life, but populations of a given seagrass species can themselves be very genetically diverse and this diversity itself is linked to higher animal abundances. Understanding how seagrass genotypic diversity does this is an active area of research.

Foundation of Coastal Food Webs

Seagrass beds are important feeding grounds for thousands of species around the world, and they support this diverse food web in three different ways. Some organisms-primarily large grazers like manatees, dugongs, green sea turtles and geese-eat the living leaves directly, and seagrass forms a major component of their diets. For example, an adult dugong eats about 64 to 88 pounds (28 to 40 kg) of seagrass a day, while an adult green sea turtle can eat about 4.5 pounds (2 kg) per day. Many of these large grazers are endangered, in large part because of habitat destruction and hunting, but once they were very common. It's estimated that before Europeans settled the Americas in the 1400's, the number of green sea turtles supported by seagrass meadows was 15 to 20 times the number and biomass of large hooved animals in the Serengeti Desert alive today. These abundant large grazers probably kept seagrass meadows cropped short like a putting green.

The epiphytic organisms growing on the surface of the seagrass blades provide other sources of food. Some epiphytic bacteria can extract nitrogen from the environment and make it available to larger animals. Small invertebrate mesograzers, such as crustaceans and snails, feed on epiphytes, and in doing so can help keep the seagrass clean, acting as mutualistic partners (or housekeepers) that promote seagrass growth. They are in turn consumed by larger crustaceans, fish and birds and are important links in the coastal food web. But, this partnership isn't always positive. Occasionally when some mesograzer species are at very high densities they can create thick masses of mucus and sediment tubes that block light to the seagrass leaves, and they can even eat the seagrass directly.

Dead seagrass leaves also play an important role in coastal ecosystems. When the leaves die, they decay on the sediment or are washed onto the beach, supporting a diverse community of decomposers that thrive on rotting material. Some of these living and dead seagrass blades are also washed to other areas of the ocean, feeding organisms in ecosystems as far as the deep sea.
Small invertebrates, such as these crustaceans (left) and gastropods (right), can help keep seagrasses clean by consuming epiphytic algae. Photos (clockwise from top left) by Chris Nicolini, Matt Whalen, Jonas Thormar and Camilla Gustafsson

Blue Carbon

Seagrasses are capable of capturing and storing a large amount of carbon from the atmosphere. Similar to how trees take carbon from the air to build their trunks, seagrasses take carbon from the water to build their leaves and roots. As parts of the seagrass plants and associated organisms die and decay, they can collect on the seafloor and become buried, trapped in the sediment. It has been estimated that in this way the world's seagrass meadows can capture up to 83 million metric tons of carbon each year. The carbon stored in sediments from coastal ecosystems including seagrass meadows, mangrove forests and salt marshes is known as "blue carbon" because it is stored in the sea. While seagrasses occupy only 0.1 percent of the total ocean floor, they are estimated to be responsible for up to 11 percent of the organic carbon buried in the ocean. One acre of seagrass can sequester 740 pounds of carbon per year (83 g carbon per square meter per year), the same amount emitted by a car traveling around 3,860 miles (6,212 km).

Threats & Conservation

Unfortunately, seagrasses are in trouble. Seagrass coverage is being lost globally at a rate of 1.5 percent per year. That amounts to about 2 football fields of seagrass lost each hour. It's estimated that 29 percent of seagrass meadows have died off in the past century. In a 2011 assessment, nearly one quarter of all seagrass species for which information was adequate to judge were threatened (endangered or vulnerable) or near threatened using the International Union for the Conservation of Nature (IUCN) Red List criteria. This is especially worrying because seagrass losses are projected to have severe impacts on marine biodiversity, the health of other marine ecosystems, and on human livelihoods. Additionally, some threatened marine species such as sea turtles and marine mammals live in seagrass habitats and rely on them for food. For every seagrass species there is on average more than one associated threatened marine species. In fact, the only marine plant listed as endangered in the United States is a seagrass (Halophila johnsonii) found in Florida.

Threats to Seagrasses

(Antoine N'Yeurt, Moorea Biocode Project )

Seagrasses are vulnerable to physical disturbances, such as wind-driven waves and storms. Some animals, such as skates and rays, disturb the rhizomes and roots of seagrasses, ripping up the seagrass as they forage for buried clams and other invertebrates. However, the direct and indirect effects of human activities account for most losses of seagrass beds in recent decades. Some fast growing seagrass meadows are able to rebound from disturbances, but many grow slowly over the course of centuries and are likely to be slow to recover and are thus most vulnerable.

Nutrients, such as those from fertilizers and pollution, wash off the land and into the water, causing algal blooms that block sunlight necessary for seagrass growth. Sediment washing into the water from agriculture and land development can also damage seagrass beds by both smothering the seagrass and blocking sunlight. Similarly, dredging can both directly remove seagrass plants and cause lower light levels because of increased amounts of sediments in the water. Boat anchors and propellers can leave "scars" in a seagrass bed-killing sections of the seagrass and fragmenting the habitat. This fragmentation of seagrass beds can increase erosion around the edges, as well as influence animal use and movement within the seagrass bed.

Disease has also devastated seagrasses. In the early 1930s, a large die-off of up to 90 percent of all eelgrass (Zostera marina) growing in temperate North America was attributed to a "wasting disease". This die-off was so severe that a small snail specialized to live on eelgrass went extinct as a result. The disease was caused by the slime mold-like protist, Labyrinthula zosterae, which also ravaged eelgrass populations in Europe. This disease still affects eelgrass populations in the Atlantic and has contributed to some recent losses, though none as catastrophic as in the 1930s. Eelgrass leaves that are weak or stressed are more susceptible to the disease, developing brown spots and lesions that reduce the plant's ability to photosynthesize, eventually killing the plant. Healthy plants are thought to be resistant to the disease, indicating importance of reducing other stressors like pollution. Lower seawater salinity may also increase susceptibility to the Labyrinthula pathogen.

Episodes of warm seawater temperatures can also damage seagrasses. Temperature affects how enzymes and metabolism work, influencing how organisms grow. Rising water temperatures tend to increase rates of seagrass respiration (using up oxygen) faster than rates of photosynthesis (producing oxygen), which makes them more susceptible to grazing by herbivores. Increased temperature also increases seagrass light requirements, influences how quickly seagrasses can take up nutrients in their environment, and can make seagrasses more susceptible to disease. Large eelgrass declines have been observed in the Chesapeake Bay in years in which water temperatures have persisted for several days above 30°C (86°F), the thermal limit for this species.

Removal of fish can also lead to seagrass death by disrupting important components of the food web. When large predators are removed, intermediate predators can become more abundant, and they in turn cause the decline of the smaller organisms that keep the blades of the seagrasses clean. This has been observed most strikingly in the Baltic sea with the disappearance of cod due to overfishing and corresponding increases in smaller fishes and crustaceans which limited epiphyte-grazing invertebrates, resulting in seagrass decline.

In addition to the small epiphytic algae, larger algae also compete with seagrasses, and introduced invasive seaweed species can displace native seagrass species. One important example is the invasion of Caulerpa taxifolia, a seaweed nicknamed "the killer algae." Released into the Mediterranean in the 1980s from aquaria, by 2000 it covered more than 131 square kilometers (50 square miles) of the Mediterranean coastline, overgrowing and replacing the native Neptune seagrass (Posidonia oceanica) and reducing the ecosystem's biodiversity. Since then, invasive Caulerpa has been found in California and southwestern Australia where eradication programs are in place to prevent its spread.

Protecting and Restoring Seagrass Beds

(Gaynor Rosier/Marine Photobank)

Most management that protects seagrasses focuses on maintaining their biodiversity and the services these habitats provide for humans and ecosystems. There is no international legislation for seagrasses, and so protection typically occurs by local and regional agencies. Actions taken to help seagrasses include limiting damaging practices such as excessive trawling and dredging, runoff pollution and harmful fishing practices (such as dynamite or cyanide fishing).

There are also attempts to rebuild and restore seagrass beds, often by planting seeds or seedlings grown in aquaria, or transplanting adult seagrasses from other healthy meadows. Some of the most successful restoration stories come from the Chesapeake Bay and coastal Virginia in the Eastern United States where, through 2014, the Virginia Institute of Marine Science has seeded 456 acres with 7.65 million seagrass seeds. As of 2015, the seagrass Zostera marina has increased from these seeded plots to cover 6,195 acres. Seagrass restoration in Tampa Bay, Florida, has also experienced important success including improvements in water quality and the associated fish community. For restoration to work, it is critical that the causes of the original decline in seagrasses have been eliminated.

However, seagrass populations globally are still in trouble. Some simple steps everyone can take to help seagrasses and other marine habitats include: don't litter, limit the amount of fertilizer and pesticides you use, don't dump anything hazardous down the drain, be careful when boating by going slow and avoiding shallow areas, and support local conservation efforts.

Seagrass at the Smithsonian

(Jonas Thormar)

Because of their ecologic importance and global distribution, seagrass are important study systems for understanding how coastal habitats work and respond to environmental changes. A network of scientists are using the seagrass Zostera marina as a model species to test how biodiversity-the number of types of animal species and genetically different plants-may help protect these important plants against threats such as pollution and overfishing. Called the Zostera Experimental Network (ZEN), this program was initiated in 2011 by the Smithsonian Institution's Tennenbaum Marine Observatories Network director Dr. Emmett Duffy. These scientists conduct coordinated, simultaneous surveys and experiments in eelgrass habitats at 50 locations across the Northern Hemisphere to address those questions. The newer Thalassia Experimental Network (TEN), run by scientists working with the Smithsonian Institution's MarineGEO program, uses similar approaches to test those questions in tropical Thalassia testudinum habitats in the Florida Keys, Panama and Belize. Additionally, SeagrassNet monitors 122 seagrass beds across the world to track patterns in seagrass health. By working together, these international science teams hope to not only understand how these critical coastal habitats work, but how to best protect them and ensure their existence in the future.

Additional Resources

Seagrass Habitats at Indian River Lagoon - Smithsonian Marine Station at Fort Pierce

Economic Values of Coral Reefs, Mangroves, and Seagrasses - A Global Compilation 2008 (PDF)

Importance of Seagrass - Florida Fish and Wildlife Conservation Commission
ZEN (Zostera Experimental Network)
Seagrass Educators Handbook (PDF) - Seagrass Watch

News Articles:
Seagrass: unsung ecological hero, potential economic powerhouse (The Science Show)
New report enables creation of carbon credits for restored wetlands (Smithsonian Science News)
Seagrass Restoration Paying Off for Eastern Shore (UVA Today)
Carbon capture and storage: Seagrasses do it for free (ABC)

Books:
Seagrass Ecology by M. Hemming and C.M. Duarte
Seagrasses: Biology, ecology and conservation by A.W.D. Larkum, R.J. Orth and C.M. Duarte
Global Seagrass Research Methods edited by F.T. Short and R.G. Coles
World Atlas of Seagrasses by E.P. Green and F.T. Short

Scientific Papers:
Global seagrass distribution and diversity: A bioregional model - F. Short, T. Carruthers, W. Dennison, and M. Waycott
Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach - J.E. Duffy, P.L. Reynolds, C. Boström, et al.
A Global Crisis for Seagrass Ecosystems - Robert Orth, Tim Carruthers, William Dennison, et al.
The value of the world's ecosystem services and natural capital (PDF) - Robert Costanza, Ralph D'Arge, Rudolf de Groot, et al.
Extinction risk assessment of the world's seagrass species - Frederick T. Short, Beth Polidoro, Suzanne R. Livingstone, et al.

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Home Ocean Life Plants & Algae Seagrass and Seagrass Beds Seagrasses are found in shallow salty and brackish waters in many parts of the world, from the tropics to the Arctic Circle. Seagrasses are so-named because most species have long green, grass-like leaves.

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Duckster

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Kids learn about the freshwater aquatic biome. Ecosystems such as rivers, streams, ponds, lakes, wetlands, swamps, and bogs.

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What’s so great about the Great Lakes? - Cheri Dobbs and Jennifer Gabrys

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com

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Science for Kids: Temperate Forest Biome

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Kids learn about the temperate forest biome. Four distinct seasons and lots of trees.

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Planting mangroves in Thailand | Global 3000

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Fabulous Wetlands with Bill Nye The Science Guy (1989)

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MooMoo Math and Science

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MooMoo Math and Science

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World Biomes: Temperate Deciduous Forest

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World Biomes: Temperate Deciduous Forest

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MooMoo Math and Science

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Arctic Foxes... Read More ...and Polar Bears... Read More ...At TundraAnimals.Net Read More Animals Mammals Arctic Fox Arctic Hare Caribou ...

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Kids learn about the tundra grasslands biome. This cold and dry ecosystem is located far to the north.

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National Geographic

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Arctic and Alpine Tundra-Tundra information

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Mangroves are among the oldest and most productive wetland forests on our planet. Found in the intertidal zone, they are uniquely adapted to survive highly saline and anoxic conditions. They are ideal habitats for many terrestrial and marine species, carbon sinks and natural barriers against storm surges and coastal erosion.

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Costa Rican Catepillars, Mexican Wildcats, and Brazilian River Otters

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This index page of a curricular unit about endangered ecosystems provides links to the various student projects and activities. As part of this unit students learn about the Earthwatch Site, participate in a virtual interactive food web, and build a caterpillar using online interactive technology. A link to a useful teacher's guide is included.

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Defenders is fighting for clean water protections throughout the country, and especially in the Southeast, which is a hotspot of freshwater biodiversity. We are bringing enforcement lawsuits against polluters for illegally discharging pollutants from coal ash landfills and other point-source pollution.

Defenders is also a member of several coalitions and partnerships throughout the Southeast to protect and restore the health of streams and rivers for all freshwater wildlife, including the fourteen-state Wetland Forest Initiative.

In the Northwest, we are advocating ways to reduce pollution in the Salish Sea with our Orcas Love Raingardens program and remove outdated dams from rivers in the region to restore salmon.

We are relocating "nuisance" beavers in the Rockies and Plains to promote healthy wetlands and waterways and provide habitat for other aquatic species.

We are also working across the country to protect aquatic connectivity for freshwater fish, mussels, turtles and amphibians that need to move between habitats for breeding or because of climate change-induced temperature increases.

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Wetlands are the link between land and water and are some of the most productive ecosystems in the world. Depending on the type of wetland, it may be filled mostly with trees, grasses, shrubs or moss. Some wetlands, like vernal pools, are actually dry at certain times of the year.

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Amazing Ways to Live in the Desert

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Meerkats... Read More ...and Horned Lizards... Read More ...At DesertAnimals.Net Read More Desert Animals Mammals Black-Tailed Jackrabbit Caracal Fennec Fox ...

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Food Webs, Examples of food webs found in different habitats around the world.

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In this report you will learn about Hot and Dry Deserts and Cold Deserts. I hope you enjoy!

A Hot and Dry Desert is, as you can tell from the name, hot and dry. Most Hot and Dry Deserts don't have very many plants. They do have some low down plants though. The only animals they have that can survive have the ability to burrow under ground. This is because they would not be able to live in the hot sun and heat. They only come out in the night when it is a little cooler.

A cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and Dry Deserts.

Deserts cover about one fifth of the Earth's land surface. Most Hot and Dry Deserts are near the Tropic of Cancer or the Tropic of Capricorn. Cold Deserts are near the Arctic part of the world.

Hot and Dry Deserts temperature ranges from 20 to 25° C. The extreme maximum temperature for Hot Desert ranges from 43.5 to 49° C. Cold Deserts temperature in winter ranges from -2 to 4° C and in the summer 21 to 26° C a year

The precipitation in Hot and Dry Deserts and the precipitation in Cold Deserts is different. Hot and Dry Deserts usually have very little rainfall and/or concentrated rainfall in short periods between long rainless periods. This averages out to under 15 cm a year. Cold Deserts usually have lots of snow. They also have rain around spring. This averages out to 15 - 26 cm a year.

Hot and Dry Deserts are warm throughout the fall and spring seasons and very hot during the summer. the winters usually have very little if any rainfall. Cold Deserts have quite a bit of snow during winter. The summer and the beginning of the spring are barely warm enough for a few lichens, grasses and mosses to grow.

Hot and Dry Deserts vegetation is very rare. Plants are almost all ground-hugging shrubs and short woody trees. All of the leaves are replete (packed with nutrients). Some examples of these kinds of plant are Turpentine Bush, Prickly Pears, and Brittle Bush. For all of these plants to survive they have to have adaptations. Some of the adaptations in this case are the ability to store water for long periods of time and the ability to stand the hot weather.

Cold Desert's plants are scattered. In areas with little shade,about 10 percent of the ground is covered with plants. In some areas of sagebrush it reaches 85 percent. The height of scrub varies from 15 cm to 122 cm. All plants are either deciduous and more or less contain spiny leaves.

Hot and Dry Deserts animals include small nocturnal (only active at night) carnivores. There are also insects, arachnids, reptiles, and birds. Some examples of these animals are Borrowers, Mourning Wheatears, and Horned Vipers. Cold Deserts have animals like Antelope, Ground Squirrels, Jack Rabbits, and Kangaroo Rats.

Stetson N. 2000
Bibliography:
Lambert, Wayne, "Deserts", The World Book Encyclopedia, 1994 ed.

Critchfield, Howard J., "Deserts", The New Book of Knowledge, 1998 ed.

"Deserts". http://www.ucmp.berkeley.edu/glossary/gloss5/deserts.html, (5/30/00)

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In this report you will learn about Hot and Dry Deserts and Cold Deserts. I hope you enjoy! A Hot and Dry Desert is, as you can tell from the name, hot and dry. Most Hot and Dry Deserts don't have very many plants. They do have some low down plants though.

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Grassland biomes are large, rolling terrains of grasses, flowers and herbs. Latitude, soil and local climates for the most part determine what kinds of plants grow in a particular grassland. A grassland is a region where the average annual precipitation is great enough to support grasses, and in some areas a few trees. The precipitation is so eratic that drought and fire prevent large forests from growing. Grasses can survive fires because they grow from the bottom instead of the top. Their stems can grow again after being burned off. The soil of most grasslands is also too thin and dry for trees to survive.

When the settlers of the United States moved westward, they found that the grasslands, or prairies as they called them, were more than just dry, flat areas. The prairies contained more than 80 species of animals and 300 species of birds, and hundreds of species of plants.

There are two different types of grasslands; tall-grass, which are humid and very wet, and short-grass, which are dry, with hotter summers and colder winters than the tall-grass prairie. The settlers found both on their journey west. When they crossed the Mississippi River they came into some very tall grass, some as high as 11 feet. Here it rained quite often and it was very humid. As they traveled further west and approached the Rocky Mountains, the grass became shorter. There was less rain in the summer and the winters got colder. These were the short-grass prairies.

Grassland biomes can be found in the middle latitudes, in the interiors of continents. They can have either moist continental climates or dry subtropical climates. In Argentina, South America, the grasslands are known as pampas. The climate there is humid and moist. Grasslands in the southern hemisphere tend to get more precipitation than those in the northern hemisphere, and the grass tends to be the tall-grass variety.

There is a large area of grassland that stretch from the Ukraine of Russia all the way to Siberia. This is a very cold and dry climate because there is no nearby ocean to get moisture from. Winds from the arctic aren't blocked by any mountains either. These are known as the Russian and Asian steppes.

In the winter, grassland temperatures can be as low as -40° F, and in the summer it can be as high 70° F. There are two real seasons: a growing season and a dormant season. The growing season is when there is no frost and plants can grow (which lasts from 100 to 175 days). During the dormant (not growing) season nothing can grow because its too cold.

In tropical and subtropical grasslands the length of the growing season is determined by how long the rainy season lasts. But in the temperate grasslands the length of the growing season is determined by temperature. Plants usually start growing when the daily temperature reached about 50° F.

In temperate grasslands the average rainfall per year ranges from 10-30 inches. In tropical and sub-tropical grasslands the average rainfall per year ranges from 25-60 inches per year The amount of rainfall is very important in determining which areas are grasslands because it's hard for trees to compete with grasses in places where the uppers layers of soil are moist during part of the year but where deeper layer of soil are always dry.

The most common types of plant life on the North American prairie are Buffalo Grass, Sunflower, Crazy Weed, Asters, Blazing Stars, Coneflowers, Goldenrods, Clover, and Wild Indigos.

Some common animals in the grasslands are Coyotes, Eagles, Bobcats, the Gray Wolf, Wild Turkey, Fly Catcher, Canadian Geese, Crickets, Dung Beetle, Bison, and Prairie Chicken.

by Sam M. 2000
Bibliography:
Living In The Environment: An Introduction To Environmental Science G. Tyler Miller--20th edition; Wadsworth Publishing, Belmont, California,

Encyclopedia Britannica, 20th Edition

"Temperate Grasslands" http://www.runet.edu/~swoodwar/CLASSES/GEOG235/biomes/tempgrass/tempgras.html, (Oct. 2000).

"Grasslands",
http://www.ucmp.berkeley.edu/glossary/gloss5/biome/grasslan.html, (Oct. 2000).

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Grassland biomes are large, rolling terrains of grasses, flowers and herbs. Latitude, soil and local climates for the most part determine what kinds of plants grow in a particular grassland. A grassland is a region where the average annual precipitation is great enough to support grasses, and in some areas a few trees.

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Famous Rainforests

There are rainforests in Africa, Asia, Australia, and Central and South America. The biggest rainforest is the Amazon rainforest. It's about the size of the contiguous United States, which doesn't include Alaska or Hawaii. More than half of it is in Brazil, but parts are in several other South American countries, including Ecuador and Bolivia. The next biggest rainforest is the Congo in Africa. Parts of the Congo can be found in several other countries too, including the Democratic Republic of Congo and Cameroon.

Most rainforests are found along or near the Equator, where it tends to be hot. But some rainforests grow in temperate regions where it's cooler. Hoh Rainforest in Olympic National Park on the Pacific northwest coast of North America is an example of a temperate rainforest. Like tropical rainforests, temperate rainforests get lots of, well, rain.

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Famous Rainforests There are rainforests in Africa, Asia, Australia, and Central and South America. The biggest rainforest is the Amazon rainforest. It's about the size of the contiguous United States, which doesn't include Alaska or Hawaii. More than half of it is in Brazil, but parts are in several other South American countries, including Ecuador and Bolivia.

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When you think of a desert, what do you imagine? Perhaps you imagine the saguaros of the Sonoran Desert in Arizona. Maybe you think of the camels and sand dunes found in the Sahara Desert in Africa. Both of these images are correct, but did you know that deserts can also be cold?

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Smithsonian's National Museum of Natural History

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Mangroves, Biodiversity

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Mongabay Kids - the nature and conservation corner for kids

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A herd of antelope moves slowly through the tall grass. Suddenly a cheetah leaps from its hiding place, and the animals zig and zag across the savanna. They make it to a small grove of scrubby trees, but they can't let their guard down yet. It's the end of the rainy season and the antelopes-like many animals on the grasslands-must leave their protected place and migrate across open grasslands to find water.

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A herd of antelope moves slowly through the tall grass. Suddenly a cheetah leaps from its hiding place, and the animals zig and zag across the savanna. They make it to a small grove of scrubby trees, but they can't let their guard down yet.

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'Zombie' Parasite Cordyceps Fungus Takes Over Insects Through Mind Control | National Geographic

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Amazing Symbiosis: Ant Army Defends Tree | National Geographic

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Ecosystem Ecology: Links in the Chain - Crash Course Ecology #7

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Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

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Understanding Ecosystems for Kids: Producers, Consumers, Decomposers - FreeSchool

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Producer Consumers - Food Chain - Kid’s Corner

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Online games and education. kids educational games. Kids Corner. Herbivore, Carnivore, Omnivore. Online learning. Animal diet. Free online games for kids.

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Each ecosystem has its own community. A terrarium community, for example, can have small animals. A desert community may have cacti, small snakes, and scorpions. A pond community can have frogs, insects, snakes, and plants, and a forest community may have rabbits, foxes and pine trees.

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by Sciencing

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An ecosystem is comprised of all the non-living elements and living species in a specific local environment. Components of most ecosystems include water, air, sunlight, soil, plants, microorganisms, insects and animals. Ecosystems may be terrestrial - that is, on land - or aquatic. Sizes of ecosystems vary; they could entail a small puddle or an enormous swath of desert. Likewise, natural ecosystems can look quite different from one another.

Located in tropical regions, rainforests possess a greater diversity of plant and animal life than any other type of ecosystem. As their name implies, precipitation is significant, leading to dense, verdant vegetation. Trees grow very tall as they compete for sunlight, and animals live in their canopy.

Forest ecosystems are common across temperate climates - areas where winters are cold and summers are warm. They usually consist of deciduous trees, which shed their leaves each autumn, and coniferous trees, which stay green throughout the year.

Taigas are a type of forest ecosystem located in the far northern regions of the world. Also called boreal forests, they consist mainly of evergreen, coniferous trees, such as pine and spruce.

Grasslands, located in semi-arid zones, contain wide, treeless expanses often inhabited by grazing animals. Sub-categories of grassland ecosystems include savannas, which are found in the tropics; prairies, situated in temperate regions; and steppes, which can be found in either climate.

With a drier climate than grasslands, desert ecosystems are characterized by relatively sparse vegetation, and the number of insects and animals is also relatively limited. Deserts aren't necessarily hot; they can lie in temperate zones as well. Nor must they be sandy; many deserts feature rock floors.

Tundra ecosystems, located in polar regions or on the tops of high mountains, are frozen and snow-covered most of the year. Life is hard in these white, treeless swaths, but during the brief summer, snows may melt enough to expose lichens or small wildflowers and attract migrating birds.

Various aquatic ecosystems can be found in stagnant or very slowly flowing waters. Lakes, ponds, bogs, freshwater and saltwater marshes, swamps and lagoons are examples of ecosystems found in stationary or nearly-stationary waters. Algae, plankton, underwater and floating plants, such as lily pads, may inhabit the calm waters.

Consisting of flowing freshwater, river and stream ecosystems support a variety of underwater life. Their relatively fast-moving waters boast a higher oxygen content than that of stationary waters, allowing greater biodiversity among plant and animal species.

Littoral zones are essentially coastlines, the often shallow parts of the ocean nearest the shore. The waters in littoral zones experience a significant amount of turbulence, due to wave action. Seaweed, barnacles, mollusks and crabs may be found in littoral zones.

Coral reefs are often referred to as the "rainforests of the ocean" because these ecosystems teem with life - an estimated one-quarter of marine species rely on them for food or shelter. In addition to corals and brightly-colored fish, sponges, sea anemones, sea urchins and clams make their homes in coral reefs.

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Natural ecosystems are often as unique as the creatures that inhabit them. Here are ten examples of land and water ecosystems.

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by Sciencing

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An ecosystem consists of all the living and non-living things in a specific natural setting. Plants, animals, insects, microorganisms, rocks, soil, water and sunlight are major components of many ecosystems. All types of ecosystems fall into one of two categories: terrestrial or aquatic. Terrestrial ecosystems are land-based, while aquatic are water-based. The major types of ecosystems are forests, grasslands, deserts, tundra, freshwater and marine. The word "biome" may also be used to describe terrestrial ecosystems which extend across a large geographic area, such as tundra. Keep in mind, however, that within any ecosystem, specific features vary widely - for instance, an oceanic ecosystem in the Caribbean Sea will contain vastly different species than an oceanic ecosystem in the Gulf of Alaska.

Forest ecosystems are classified according to their climate type as tropical, temperate or boreal. In the tropics, rainforest ecosystems contain more diverse flora and fauna than ecosystems in any other region on earth. In these warm, moisture-laden environments, trees grow tall and foliage is lush and dense, with species inhabiting the forest floor all the way up to the canopy. In temperate zones, forest ecosystems may be deciduous, coniferous or oftentimes a mixture of both, in which some trees shed their leaves each fall, while others remain evergreen year-round. In the far north, just south of the Arctic, boreal forests - also known as taiga - feature abundant coniferous trees.

Different types of grassland ecosystems can be found in prairies, savannas and steppes. Grassland ecosystems are typically found in tropical or temperate regions, although they can exist in colder areas as well, as is the case with the well-known Siberian steppe. Grasslands share the common climactic characteristic of semi-aridity. Trees are sparse or nonexistent, but flowers may be interspersed with the grasses. Grasslands provide an ideal environment for grazing animals.

The common defining feature among desert ecosystems is low precipitation, generally less than 25 centimeters, or 10 inches, per year. Not all deserts are hot - desert ecosystems can exist from the tropics to the arctic, but regardless of latitude, deserts are often windy. Some deserts contain sand dunes, while others feature mostly rock. Vegetation is sparse or nonexistent, and any animal species, such as insects, reptiles and birds, must be highly adapted to the dry conditions.

As with deserts, a harsh environment characterizes ecosystems in the tundra. In the snow-covered, windswept, treeless tundra, the soil may be frozen year-round, a condition known as permafrost. During the brief spring and summer, snows melt, producing shallow ponds which attract migrating waterfowl. Lichens and small flowers may become visible during this time of year. The term "tundra" most commonly denotes polar areas, but at lower latitudes, tundra-like communities known as alpine tundra may be found at high elevations.

Freshwater ecosystems can be found in streams, rivers, springs, ponds, lakes, bogs and freshwater swamps. They are subdivided into two classes: those in which the water is nearly stationary, such as ponds, and those in which the water flows, such as creeks. Freshwater ecosystems are home to more than just fish: algae, plankton, insects, amphibians and underwater plants also inhabit them.

Marine ecosystems differ from freshwater ecosystems in that they contain saltwater, which usually supports different types of species than does freshwater. Marine ecosystems are the most abundant types of ecosystems in the word. They encompass not only the ocean floor and surface but also tidal zones, estuaries, salt marshes and saltwater swamps, mangroves and coral reefs.

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An ecosystem consists of all the living and non-living things in a specific natural setting. Plants, animals, insects, microorganisms, rocks, soil, water and sunlight are major components of many ecosystems. All types of ecosystems fall into one of two categories: terrestrial or aquatic. Terrestrial ecosystems are land-based, while aquatic are water-based.

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by PBS

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Everything in the natural world is connected. An ecosystem is a community of living and non-living things that work together. Ecosystems have no particular size. An ecosystem can be as large as a desert or a lake or as small as a tree or a puddle. If you have a terrarium, that is an artificial ecosy…