# data[].attributes.body
Many of Japan's cities have done well in managing population density through public transportation infrastructures like their world class train system.

there are two ways to interpret the vast city crowds that result from Japan's efficient train system

Ritsuko, a woman in her late 60s loves the diversity she finds in crowds and the energy the young people have

31 yr old Toru sees loneliness within the urbanite who is engulfed with work, which seems worse when surrounded by others

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1.  Reiterate the importance of your lens-focused question.

2.  Circle back to how the three themes connect with each other AND how these themes shed light on your lens-focused question.

3.  Based on these implications, suggest how to proceed with investigating different solutions.

City density could be a problem, or could be seen as a solution depending on how we as a society tackle it. When land is utilized well, it can lead to environmental sustainability and greater community cohesiveness, however when a city is too dense and not properly managed, it can lead to disease and social isolation

Kowloon city represents the most innovative approach to city expansion, but it is without its faults

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The idea off multi use could also apply for the internet economy. By using a building to contribute to a country's GDP with the internet, it can also be used for purposes like to provide a residential space.

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TRANSITION:  CONNECTION FROM THEME TO THEME

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TRANSITION:  CONNECTION FROM THEME TO THEME

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Set up your next theme by highlighting how the takeaways from the previous theme "are in conversation with" and connect with the upcoming theme.

the cleanliness exhibited in Tokyo's neighborhoods is hard to implement worldwide. If not done properly, the ultra high density can lead to the spread of diseases and the continuation of poor sanitation

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TRANSITION:  CONNECTION FROM THEME TO THEME

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TRANSITION:  CONNECTION FROM THEME TO THEME

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Set up your next theme by highlighting how the takeaways from the previous theme "are in conversation with" and connect with the upcoming theme.

Methods of land use can have environmental benefits, but they can have benefits in concepts that are not as easily measured such as community connection.

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1. How do these sources, and your connections between these sources, provide meaningful information in regards to your chosen theme and how that theme relates to your specific RQ?

though density in cities may lead to better social connections, it can lead to greater health concerns. Also, the way a city expands can give insight to its economy and help better inform planners on what to do in order to help its environmental sustainability for the future

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disease can be an indicator of poor management of densely populated cities. Tokyo doesn't exhibit it but both Kowloon and some cities and India share the same behavior

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Kowloon has the most interesting city development in the sense that it doesn't expand traditionally like highlighted in the 4th source. It expands organically and could be an insight in a potential solution

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height causes more population inflow which further increases heights of buildings

decrease in horizontal travel cost leads to horizontal expansion

laws and land designation affect city development in general

-come back to this source it has very in depth analysis

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Abstract

We document that skyscraper growth since the end of the 19 century has been driven by a reduction in the cost of height, increasing urbanization, and rising incomes. These stylized facts guide us in developing a competitive open-city within cities; (ii) the causal relationship between skyscrapers and urbanization is bi-directional; and (iii) height limits reduce the size of large cities, leading to lower th general equilibrium model of vertical and horizontal city structure. We use the model to show that (i) vertical costs and benefits affect the horizontal land use pattern agglomeration economies, productivity, and urban GDP. We substantiate the model's predictions by novel estimates of urban height gradients.

Introduction

The study of the horizontal structure of urban space has been one of the main research areas in urban economics ever since the birth of the field (Alonso, 1964, Mills, 1967, Muth, 1969). While iconic skylines have long become distinctive features of cities over the course of the 20 th century, it is not until recently that urban economics research into the vertical structure of cities has gained momentum.

We bring together recent research on costs (Ahlfeldt, McMillen, 2018, Barr, 2010) and benefits (Barr, 2016, Liu, Rosenthal, Strange, 2018, Liu, Rosenthal, Strange, 2020) of building height, which we integrate into a general equilibrium model of the vertical and horizontal structure of an open city. We use the model to engage with the following questions concerning the positive and normative economics of skyscrapers: How do vertical costs and benefits shape the internal structure of cities? How does the distribution of economic activity between cities and rural hinterlands affect the vertical size of cities and vice versa? What are the consequences of distortionary policies that constrain the vertical size of cities on the spatial distribution of economic activity and welfare? We complement our theoretical analyses with novel evidence on urban height gradients to guide our modeling choices and confirm the model's predictions. From our theoretical and empirical analyses, as well as our reading of the literature, we conclude that vertical costs and benefits, horizontal land use patterns, urban growth, and welfare are all mutually dependent in ways that leave plenty of room for future research.

In developing a model that integrates vertical and horizontal spatial structure, we must engage with the obvious question of how skyscrapers emerge. ¹ Therefore, we start by exploiting a unique data set that blends building-level data from commercial and non-profit providers covering the entire planet and hand-collected data for selected cities spanning 150 years (see Online Appendix Section A for details) to produce a battery of stylized facts that speak to the determinants of building height. We show that since 1900, there were waves of skyscraper development when there were innovations in construction technology and where there was economic growth. With few exceptions, the tallest skyscrapers today are not outliers within the skylines of their host cities. Even the Empire State Building, which ruled the height ranking for longer than any other building, delivered a decent return on investment over its lifetime. Our conclusion is that the canonical approach that assumes profit-maximizing developers in a competitive market provides a reasonable description of height decisions, even for most tall buildings.

With this in mind, we have developed a new general equilibrium model of vertical and horizontal city structure to study the causes and effects of vertical growth. To engage with our main research questions, we design the model to serve three purposes. First, the model should rationalize the remarkable differences in building heights within cities that are characteristic of metropolitan skylines and account for how use-specific vertical costs and benefits affect the horizontal land use pattern. Second, the model should address the mechanisms that drive the close relationship between urbanization, vertical growth, and rising incomes between cities, which we document in our data. Third, the model should be suitable for the evaluation of a common form of land use regulation that constraints vertical space: building height limits. Here, we are interested in the effects that this distortionary policy has on the spatial allocation of economic activity within and between cities.

Our basic set up is an open-city model (Roback, 1982) with endogenous land use (Duranton and Puga, 2015) and returns to agglomeration in the form of higher productivity. We borrow the supply side of land markets from Ahlfeldt and McMillen (2018), i.e., we impose that the marginal cost of supplying one unit of floor space increases in height at a use-specific elasticity (Barr, 2010). Thus, the model features a labor market related agglomeration force in the form of higher wages and a housing market related dispersion force in the form of higher rents. ² As for the geography, we consider a linear city where residential and production amenities differ across both horizontal and vertical space. We summarize accessibility benefits by a monotonic function of distance from a historic core and allow for greater production and residential amenity values at higher floors to rationalize recent evidence on positive vertical rent gradients (Liu, Rosenthal, Strange, 2018, Danton, Himbert, 2018).

Perfect competition among firms and perfect mobility of residents leads to perfect spatial arbitrage so that differences in amenities map into differences in rents in horizontal and vertical space. Profit-maximizing developers respond to higher rents by building taller. Perfect competition results in full capitalization of developer profits in land rents. Land is allocated to the use that generates the highest land rent, pinning down the endogenous size of the central business district (CBD) and the residential zone. In equilibrium, the city-specific wage and population, as well as location-specific floor space rents adjust such that labor and land markets clear and the utility within the city equates to the exogenous reservation utility. In this setting, an exogenous change in any parameter will generally lead to adjustments in all endogenous outcomes. Hence, the model is well suited to account for the mutual dependence of use-specific vertical costs and benefits, horizontal patterns of land use, and the size and productivity of a city.

Before we can use the model to quantitatively evaluate these mutual dependencies, we need to settle on canonical values for the model's structural parameters. Two of them deserve particular empirical attention because evidence is scarce: The height elasticity of per-unit construction cost and the height elasticity of per-unit floor space rent, which impact the costs of and returns to height. For the former, we estimate a range from 0.1 for smaller structures to 0.25 for tall commercial and 0.56 for tall residential structures. For the latter, we estimate a value of about 0.07 for residential units in New York City, as well as in Chicago. For New York City, we estimate a value of 0.033 for commercial rents. These estimates reveal that the costs of, as well as the returns to, height are greater for residential than for commercial land use. ³

The importance of accounting for such use-specific differences to understand the urban height gradient becomes apparent in the first application of our model. Under the baseline parametrization, the model delivers canonical height and rent gradients that are downward-sloping in distance from the city center and a central business district (CBD) surrounded by a residential zone (Duranton and Puga, 2015). The lower net-cost of height for commercial buildings results in steeper commercial height and land rent gradients. Importantly, we obtain the novel prediction that the commercial and residential land bid rents intersect nearer to the center than the floor space rent gradients. This pushes the CBD boundaries inwards and generates discontinuities in the height and the floor space gradients at the edge of the CBD. Hence, our model rationalizes why tall CBDs often stand out relative to the surrounding residential zones through endogenous mechanisms and without requiring exogenous zoning or spatial discontinuities in the distribution of amenities.

The model predictions for the height gradient are consistent with patterns that we find in the data. We estimate an elasticity of building height with respect to distance from a "prime location" (business centers identified by Ahlfeldt et al., 2020) of about -0.25 for a global set of cities in 1900 and 2015. It appears that demand-side forces pushing for a flatter height gradient and supply-side forces pushing for a steeper height gradient have largely offset each other in their effect on the slope of the urban height gradient over the 20 th century. Our estimates confirm that commercial rent gradients are steeper than their residential counterparts. We also find evidence for a discontinuity in the height gradient at the edge of CBDs. Conditional on smooth gradients inside and outside the boundary, there is a jump in building heights of slightly more than 20% as one steps into the CBDs of the U.S. cities in our data. Finally, we discretize space and solve for the distributions of residential and commercial amenity under which the model matches the land use pattern and the skyline of Chicago. We find that small differences in the amenity value are able to rationalize a fuzzy height gradient with large differences in building heights. Under the inverted amenity values, the model generates a distribution of land values that closely resembles observed data, lending support to the parametrization of our model.

In the second application of the model, we turn to the obvious stylized fact that skyscrapers are a big-city phenomenon. A standard prediction of urban land use models is that, because the horizontal expansion is constrained by commuting costs, a larger city size maps into greater structural density, i.e., taller buildings (Brueckner, 1987, Duranton, Puga, 2015). A separate literature advocates the reverse causality by arguing that a favorable geography (solid bedrock near the surface) facilitates the construction of tall buildings, leading to agglomeration and greater productivity (Rosenthal, Strange, 2008, Combes, Duranton, Gobillon, 2011). In a series of comparative statics that engage with major long-run trends observed over the 20 th century, we illustrate how the causal relationship between building height and city population is, indeed, bi-directional. A rise in returns to agglomeration increases the wage and attracts workers to large cities, causing skyscrapers to emerge via a demand-side channel. Similarly, a reduction in the horizontal cost of travel not only leads to a horizontal expansion, but also to a vertical expansion, since the heightened attractiveness of the city results in greater demand for floor space. In contrast, a reduction in the cost of height leads to taller buildings via a supply-side channel and lower floor space rents, which causes the city to grow until the equilibrium is restored. Hence, the sizable reduction in the cost of building tall could be an important driving force of urbanization that has gone unnoticed in a literature concerned with the growth of cities. ⁴

In the third application of the model, we evaluate how the spatial structure of cities responds to height limits. In keeping with intuition, a vertical compression leads to a horizontal expansion of the CBD. The effect on the residential zone, however, is the opposite. In our open-city model, the supply-driven increase in floor space rents leads to out-migration until an equilibrium is restored at a smaller population living on less horizontal space. The wage level falls owing to smaller agglomeration economies and, eventually, rents fall below the free-market equilibrium to restore the reservation utility. Our model predictions substantiate a popular notion in the literature that height regulation can have large and negative welfare consequences (Glaeser et al., 2005); yet, they also reveal that, if workers are mobile, relaxing height restrictions in the most expensive cities may have smaller impacts on affordability than advocates may wish for (Glaeser et al., 2005), at least in the long-run. ⁵

The remainder of the paper is organized as follows. Section 2 introduces our data and provides stylized facts that motivate some of the choices that we made when developing our model in Section 3. Section 4 discusses our choices of parameter values. Section 5 compares the model predictions for vertical and horizontal spatial structure with the evidence. Section 6 uses the model to explore the reciprocal relationship between urbanization and vertical growth. Section 7 analyzes the impacts of height caps on welfare and the vertical and horizontal urban structure. Section 8 concludes by summarizing some priority areas for future research. For the interested reader, we complement each section in this paper with a dedicated section in the online appendix in which we provide further theoretical and empirical analyses, discuss the related literature in more detail, and suggest directions for future research.

Section snippets

Data sets and stylized facts

Before we develop our model of vertical and horizontal structure in Section 3, it is useful to review some stylized facts that suggest that a conventional competitive model with an emphasis on profit-maximization is a reasonable description of height decisions. We find that vertical growth appears to be a rational response to changing demand and supply conditions. Suspiciously-tall buildings, whose height is likely determined by non-economic motives, appear to be the exception rather than the

Model

Guided by the stylized facts introduced in Section 2, we now develop a general equilibrium model of urban land use. The model features various canonical elements of standard land use models reviewed by Duranton and Puga (2015). The novel element is that we integrate use-specific vertical costs and benefits into an open-city model in which wages, population, and land use are endogenously determined. Our aim is to demonstrate how the interplay of demand for space and use-specific net-costs of

Vertical and horizontal city structure

In this section, we solve our model to derive the vertical and horizontal structure of a stylized city. We contrast the predictions for the height gradient with novel evidence from a large set of cities around the world. For a review of the related literature, as well as a discussion of potential for future research, we refer to Online Appendix Section F.

Skyscrapers as causes and effects of agglomeration

Empirically, skyscrapers appear to be a distinctively urban phenomenon (see Section 2). Therefore, it is surprising that little research has been done to establish the relationship between urbanization and vertical growth in a systematic and robust manner. In this section, we explore theoretically and empirically how cities expand into the vertical dimension as the level of agglomeration increases and reductions in the cost of height foster agglomeration. For a review of the related literature,

Height regulation

So far, we have treated land markets as competitive and unregulated. Of course, cities impose various forms of zoning and building regulations that affect height decisions (Brueckner and Sridhar, 2012). In this section, we first use our model from Section 3 to derive how height limits change the vertical and horizontal structure of a city (Section 7.1). We then turn to the welfare implications and how our open-city approach complements recent research that-implicitly or explicitly-refers to the

Conclusion

One high-level conclusion of our synthesis is that the literature engaging with the economics of tall buildings is still at an early stage. We discuss the potential future research throughout Online Appendix Sections B to H. Here, we offer an admittedly subjective selection of three priority areas for research into the vertical dimension of cities.

First, there is a long way to go in understanding how the positive and negative externalities associated with tall buildings play out on balance.

CRediT authorship contribution statement

Gabriel M. Ahlfeldt: Conceptualization, Formal analysis, Writing - original draft. Jason Barr: Conceptualization, Formal analysis, Writing - original draft.

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The economics of skyscrapers: A synthesis

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We document that skyscraper growth since the end of the 19th century has been driven by a reduction in the cost of height, increasing urbanization, an...

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1. How do these sources, and your connections between these sources, provide meaningful information in regards to your chosen theme and how that theme relates to your specific RQ?

densely populated spaces have two sides to the coin, they often better support human connections at the certain costs of other things which will be analyzed later. If the human connection is not emphasized though, it can lead to a sense of isolation among a crowd.

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however when focused around family, the dense populations found in the city help foster connections within, with each age group, not just young or old contributing

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Reducing greenhouse gas emissions is key for environmental sustainability and modern practices like internet use and 3d printed houses both help that

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1. How do these sources, and your connections between these sources, provide meaningful information in regards to your chosen theme and how that theme relates to your specific RQ?

These sources demonstrate and agree in unison that there are many ways to promote environmental sustainability by showing various methods of land use. Though they may not be perfect, they are a step in the right direction

Both sources 1 and 9 bring up the idea of compacting a lot of function within a space

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Both sources offer new methods of housing and building construction that positively impact the environment. Both could also have the potential to keep communal spaces compact which may be a good or a bad thing.

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Highlight the relationship between these two sources and how they are in conversation with one another.

Furthermore, accentuate how the implications of this connection better help the audience understand the theme and its relationship to your RQ.

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(w/LENS) How do certain methods of land use affect environmental sustainability and social connections within a densely populated city?

environmental, future, cultural and social

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Southeast Asian cities are experimenting with going back to more traditional materials like bamboo and wood to build houses.

these are environmentally sustainable and actually keep the property value low, which keeps communities tighter by staving off gentrification

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"a 1% increase in the Internet economy indexes causes a 0.135% decrease in CO2 emissions"

increase in internet use also reduces the demand for transportation

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tuberculosis has become a problem among some densely populated cities in India like Mumbai

antibacterial treatments can work, but many of the problems have been pinpointed to poor city development

one can see that the streets that separate the buildings are not maintained very well and seem to be dirty

sunlight seems to be an important remedy as well as well ventilated shared spaces that are kept clean

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urban farming isn't just it's own separate activity, it is a "component of urban infrastructure"

multi-use

Singapore is ranked 1st in the world for food security even though it imports 90% of its food

they also invest in areas of the city that promote farming

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Abstract

Commercial urban is typically restricted to agriculture land use, green or open spaces, or under-utilised or undeveloped land. As urbanising cities face the double threats of urban that integrate rather than separate agriculture from other land uses could be a critical adaptation for the sustainability of future cities. With less than 1% of land in agricultural use, the high-density, city-state of Singapore is testing integrative approaches to where and how food can be grown in the city. The shift toward land use multiplicity is prompting cross-agency collaboration in agriculture food insecurity and land scarcity, multi-functional policy development. The aims of this paper were to map changes in agricultural use of land and describe emerging policy trends in Singapore related to cross-agency collaboration and land use multiplicity. Given growing global attention to urban food policy, Singapore is a timely example where policies support integrated urban food production through high-tech intensification, a model AgriFood Innovation Park, and promotion of industrial and commercial land uses toward efficient and value-added activities that include urban farms. More examples of agriculture co-located with other land uses are needed to understand opportunities and challenges related to multi- or shared-use spaces particularly for tenure rights. Resolving regulatory and legal constraints will enable high and low tech farms to produce substantially more food in the city. urban land uses

With more than half the global population now living in urban places (United Nations, 2009), dependency on rural hinterlands to supply food is reaching the limits of sustainability (Bloem and de Pee, 2017). Do cities need to become more self-reliant in food production? Historically, urban planners focused on urban functions of the city; agriculture was considered a rural function and urban land was not allocated for cultivation (Mubvami and Mushamba, 2006). An oft cited reason for separation of agriculture from city land uses was for public health reasons; despite the reality that industries replacing agriculture tended to be more pollution-prone (France, 2016; Mougeot, 2000; Pothukuchi and Kaufman, 2000). In addition to displacement by industry, the planning trend prioritized uses that increased land values by converting agricultural land to residential or commercial (Sarker et al., 2019). With climate change and urbanization coupled with threats to urban food security, environmental degradation, and rising anomie among urban dwellers, there is a renewed effort to reintroduce agriculture into the city.

The high-density, city-state of Singapore is relatively food secure, ranking 1/113 on the global food security index (The Economist Group, 2019) ¹ and with a per capita income of $58,770 (US Dollar; 2018) (The World Bank, 2019). The paradox to Singapore's food security is 90% of food is imported (Singapore Food Agency, 2019). Relying on food imports to meet the majority of a nation's food demand is not unique; it reflects a global trend in high urban, high-earning, net food-importing countries such as Saudi Arabia, Japan, the United Kingdom, Germany, and the United States (Escaler et al., 2010) ²,³. The paradox is that even with strong purchasing power (i.e. imported food is affordable), limited political control over foreign sovereignties puts Singapore at risk for food availability (Diehl et al., 2018). Three quarters of land in Singapore is government owned, and the Singapore Land Authority (SLA), responsible for development and regulation of land resources, aims to increase self-sufficiency, developing a 30 by 30 Vision to grow enough food to meet 30% of demand by 2030 (Singapore Food Agency, 2019). Arable land continues to be developed, and interest in domestic food production focused on high-tech, high-producing, land-limited or land-less farms (hydroponics, vertical systems) is gaining traction. The SLA adheres to land use classifications defined by the Urban Redevelopment Authority; but, as the city-state aims to improve food security, the SLA is collaborating with other government agencies to offer entrepreneurs of non-traditional, multi-functional urban farms flexibility in land-use restrictions-targeting ways to overlap with commercial and residential uses.

Urbanising cities face the double threats of urban food insecurity and land scarcity, and multi-functional urban land uses that integrate rather than separate agriculture from other land uses could be a critical adaptation for the sustainability of future cities. With less than 1% of land in agricultural use, Singapore is testing integrative approaches to where and how food can be grown in the city. The objective of this paper was to identify trends in how Singapore's government agencies currently endeavour to collaboratively re-define and incentivize agriculture and allow overlap with other land uses. With growing global attention to urban food policy, Singapore offers a timely example of policies that support integrated urban food production. Governments that allow for multiplicity and adaptation of land uses could be more resilient to changing landscapes and needs, with the caveat that more examples of agriculture co-located with other land uses are needed to understand opportunities and challenges related to multi- or shared-use spaces particularly for tenure rights.

Food security is far reaching; it impacts economic development, public health, social equity, land use, and domestic security. Feeding urban populations is complex and dependent on how we use the land in the city (Sarker et al., 2019). Urban agriculture has been a strategy for feeding city dwellers from the earliest records of city development like the ancient Mayans to modern interpretations like Ebenezer Howard's Garden City. Although urban agriculture contributes to urban consumption requirements, practitioners and academics contest growing food in the city as a reliable and plausible strategy for feeding city residents (Morgan, 2009; Raja et al., 2008; Siegner et al., 2018). Acknowledging cities will remain reliant on food imports, Bloem and de Pee (2017) suggest enhancing rural-urban linkages to improve urban food systems. The City Region Food System is an approach to reconnect cities with hinterlands by effectively relocating agriculture in close proximity to markets served (Blay-Palmer et al., 2018; Brand et al., 2017). A City Region Food System is determined by the city's foodshed, the area of land needed to grow enough to support a particular population (Blay-Palmer et al., 2018). Because cities are unlikely to achieve self-sufficiency, the City Region Food System is increasingly important. But as city populations grow, hinterlands move farther away and foodsheds overlap, causing competition for the same rural resources. In the case of Singapore, classified 100% urban, hinterlands are located in another sovereignty's territory.

Urban agriculture is defined as the production, processing, and distribution of food that takes place "in (within) and around" cities or urban areas (Mougeot, 2000). More than growing food in the city, urban agriculture is embedded in economic, social, ecological and physical infrastructure systems of the city (van Veenhizen, 2006). Linked to city systems, urban agriculture touches issues of food security, unemployment and economic opportunity, education, habitat creation, stormwater mitigation, and other ecosystem services (France, 2016; Smith, 2013). At the same time, agriculture in, around, or outside the city can be polluting, exclusionary, marginalizing, and fail to be productive (Agrawal et al., 2003; Cole et al., 2008; Horst et al., 2017; van Veenhizen, 2006). Urban agriculture is threatened by land scarcity and insecurity due to land use competition, and is at risk for contamination by pollution emitted by vehicles, heavy metals in soils, organic chemicals, and urban sanitation (Armanda et al., 2019).

The explicit framing of urban agriculture as embedded in the urban 'system' challenges cities to address urban agriculture not as a discrete activity, but as an important component of urban infrastructure. Furthermore, land competition and rising land values in and around cities, especially in high density cities such as Singapore, has prompted a focus on increasing the food supply without increasing agricultural area. Intensification of agriculture is not a new idea, as witnessed in the Green Revolution. But, increased inputs of mineral fertilizer, agro-chemicals, and other external inputs is unsustainable and cannot be the future model. Options are emerging with new technology adoption that improves food production efficiency (Armanda et al., 2019; Smith, 2013). Many of these, including hydroponic and aquaponic systems, are well-suited to combine with other land uses. With diverse strategies and systems thinking, there is opportunity for cities to leverage services in addition to food production that urban agriculture can provide such as stormwater mitigation, building energy reduction, and soil remediation. However, the integration of urban agriculture as part of the city system requires a diverse range of technical, scientific, planning, horticultural and social expertise to be feasible and sustainable, and implications for land use planning are still being explored (Carolan, 2020; Weidner et al., 2019).

Planners are key actors for facilitating and promoting urban agriculture. Planners' perceptions are an important factor in limiting or ensuring provision through policy formulation for planning, regulating, and legislation of urban agriculture activities (McFarland, 2015). Despite this, the first article to explicitly link urban planning and food systems was only published in 2000 (Pothukuchi and Kaufman, 2000). Initially, the literature pointed to urban agriculture's potential impact on economic development, community food access and physical health, workforce retention, farmland preservation, waste management, and urban-rural development (Brinkley, 2012; Campbell, 2004; Lovell, 2010; Sonnino, 2009; van Veenhizen, 2006). More recently, the discourse has moved beyond traditional urban planning topics, with food justice and food sovereignty movements (Horst et al., 2017; Raja et al., 2017), connections to sustainability goals and ecosystem services (Specht et al., 2014; Weidner et al., 2019), and emphasis on diverse urban agriculture practices, processes, and impacts in cities around the world (Ayambire et al., 2019; Goodman and Minner, 2019; Oda et al., 2018).

In most countries in the developed world, agriculture is not recognized as an independent land-use category in municipal zoning plans (Cabannes and Maroccino, 2018). The most common inclusion is for agriculture to be a permitted land use on undeveloped or underutilized classified land. But, as governments recognize the significant role of zoning decisions on urban food supply, there are more examples of cities incorporating agriculture into urban policy as a legitimate land use (Cabannes and Ross, 2018; Verburg et al., 2013). In Chicago, Vancouver, and cities across Europe, allotment gardens are regulated as an independent land-use category with some restrictions. In San Francisco, multiple government agencies collaborate to support community gardens and other forms of agriculture on city-owned public land (Napawan, 2014). The city of Seattle adapted urban park zoning to include community gardens, made possible through multi-agency action and collaboration with public and private stakeholders (Hou and Grohmann, 2018).

Asian cities have also initiated cross-sector policies to support commercial urban agriculture. In Taiwan, with a growing community of organic food consumers (Chen, 2007), the government actively supports organic farming through grants and technical expertise. Taipei launched a "Garden City Initiative" that includes strategic and public sector investment into community, school, and rooftop gardens through creative public-civil society partnerships (Hou, 2018). Hong Kong's Rooftop Republic is an example of building-integrated agriculture. The high density urban environment, filled by buildings and roads, has provoked growing concerns about environmental issues and the need to promote sustainable urban environment. Hong Kong's green roofs have attracted much attention in recent years and are being installed on podium decks and building rooftops, designed for four main purposes: food production, active recreation, re-using waste (compost, stormwater), and educational opportunities (Hui, 2011).

These are just a few examples that illustrate the diverse ways cities have and continue to regulate and support agriculture in and around the urban boundary. City-wide strategies tend to consider wider urban food system perspectives (Haysom, 2015). To enact such approaches, it is argued that alternative urban food governance approaches are required. In a recent paper, Sarker et al. (2019) provide a framework for integrating agriculture in urban sustainability, and conclude that the most significant constraints are regulatory and legal. In other words, technology is not necessarily the factor holding urban farming back at the moment; instead it is property rights, government regulations, and a lack of financing - in part due to the former - that is preventing innovative ideas from being implemented (Foo and Teng, 2017).

Singapore is a timely example of a government testing new ways to collaborate across agencies to adapt and develop policies that integrate agriculture into the urban context as an element of ensuring food security through increased domestic production. This paper aims to map changes in agricultural use of land; to identify changes in definitions and allocation of land for agriculture in response to changing needs and priorities; and to describe how Singapore's land use policies incentivize or hinder current and future growth in commercial agriculture. We then discuss how changing pressures on the urban food system in Singapore, specifically, increased capacity to meet future needs, may drive a shift from a singular, siloed policy approach to a more adaptive, collaborative, multi-functional one.

AVA's Food Security Roadmap for Singapore

Urban food policies and programmes: an overview

Designing Urban Food Policies: Concepts and Approaches

Food Planning in Garden Cities

Researchers' approaches to evidence on urban agriculture and human health

Integrated Urban Agriculture, Precedents, Practices

Governing Urban Gardens for Resilient Cities: Examining the 'Garden City Initiative'in Taipei

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Feeding cities: Singapore's approach to land use planning for urban agriculture

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Commercial urban agriculture is typically restricted to agriculture land use, green or open spaces, or under-utilised or undeveloped land. As urbanisi...

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There was a case study in China in which it was shown that large scale 3d printed houses are viable

3d printed houses consume less water in building and release less greenhouse gases

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Environmental Footprint and Economics of a Full-Scale 3D-Printed House

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3D printing, is a newly adopted technique in the construction sector with the aim to improve the economics and alleviate environmental impacts. This study assesses the eco-efficiency of 3D printing compared to conventional construction methods in large-scale structural fabrication. A single-storey 3D-printed house was selected in the United Arab Emirates to conduct the comparative assessment against traditional concrete construction.

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Kowloon city was the ultimate slum "highrise"

it was a living labyrinth that constantly expanded organically with only one person, the mailman, knowing the way

living conditions were abysmal, flooding occurred often sanitation was bad and there was some crime, prostitution, and worst of all illegal dentists.

However, Kowloon City still shared the same close social connections we saw in the source 7 with the neighborhoods in Tokyo

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The most densely populated city on Earth had only one postman. His round was confined to an area barely a hundredth of a square mile in size. Yet within that space was a staggering number of addresses: 350 buildings, almost all between 10 and 14 stories high, occupied by 8,500 premises, 10,700 households, and more than 33,000 residents.

The city's many tall, narrow tower blocks were packed tight against each other-so tight as to make the whole place seem like one massive structure: part architecture, part organism. There was little uniformity of shape, height, or building material. Cast-iron balconies lurched against brick annexes and concrete walls. Wiring and cables covered every surface: running vertically from ground level up to forests of rooftop television aerials, or stretching horizontally like innumerable rolls of dark twine that seemed almost to bind the buildings together. Entering the city meant leaving daylight behind. There were hundreds of alleyways, most just a few feet wide. Some routes cut below buildings, while other tunnels were formed by the accumulation of refuse tossed out of windows and onto wire netting strung between tower blocks. Thousands of metal and plastic water pipes ran along walls and ceilings, most of them leaking and corroded. As protection against the relentless drips that fell in the alleyways, a hat was standard issue for the city's postman. Many residents chose to use umbrellas.

There were only two elevators in the entire city. At the foot of some of the high-rises, communal and individual mailboxes were nailed to the walls. But often the only option for the postman was to climb. Even several stories up, the maze of pathways continued: knotted arteries that burrowed into the heart of the city along interconnecting bridges and stairwells.

Sometimes the postman would reach a top floor and climb out onto the roof. Gangways and rusting metal ladders let him move quickly from building to building, before he dropped back down into the darkness. While some alleys were empty and quiet, others overflowed with life. Hundreds of factories produced everything from fish balls to golf balls. Entire corridors were coated with the fine flour dust used for making noodles. Acrid, chemical smells filled the streets that lay alongside metal and plastic manufacturers. Unlicensed doctors and dentists clustered together, electric signs hanging over their premises to advertise their services. Many patients came from outside the city, happy to pay bargain fees in return for asking no questions. Shops and food stalls were strung along "Big Well" Street, "Bright" Street and "Dragon City" Road. For the adventurous, dog and snake meat were specialties of the city.

Moving deeper, long corridors offered glimpses into smoke-filled rooms. The incessant click of mahjong tiles echoed along the walls. Gambling parlors lined up alongside strip clubs and pornographic cinemas. Prostitutes-including children-solicited in the darkness, leading clients away to backroom brothels. And everywhere there were bodies lying in the gloom. At Kwong Ming Street-known as "Electric Station"-wooden stalls sold cheap drugs. Addicts crouched down to inhale heroin smoke through tubes held over heated tinfoil. Bare rooms, enticingly referred to as "divans" were filled with prone men and women, all sunk in opium stupors. Many of the city's rats were addicts too, and could be seen writhing in torment in dark corners, desperate for a hit.

There was no law to speak of. This was an anarchist society, self-regulating and self-determining. It was a colony within a colony, a city within a city, a tiny block of territory at once contested and neglected. It was known as Kowloon Walled City. But locals called it something else. Hak Nam-the City of Darkness.

Following the first Opium War of 1839 to 1842-sparked, in essence, by the Chinese government's attempts to prevent the East India Company from importing narcotics-China signed a treaty ceding a portion of its territory to Great Britain: a near-deserted, mountainous island with a sheltered, deep-water harbor at the entrance to the Canton River, opposite the Kowloon Peninsula. Hong Kong.

In 1843, the Chinese began to build a fort at the very tip of the Kowloon Peninsula, with an office for the Mandarin (the government official) and a barracks for 150 soldiers, surrounded by a wall that was 700 feet long and 400 feet wide. Known as Kowloon Walled City, it was intended as a visible Chinese military presence near the new British colony. In 1860, disputes over trade sparked a second Opium War. British and French forces devastated the Chinese, and a new treaty granted the whole of the Kowloon Peninsula to Britain, with a solitary exception-the Walled City.

Over the next 30 years, British authorities attempted to negotiate control of the city, but the Chinese remained firm. Even a new treaty in 1898, which granted Hong Kong, Kowloon, and further territories in Canton to Britain for 99 years, kept the Walled City under Chinese control. A year later, in May 1899, rumors circulated that Chinese soldiers were massing again in the Walled City, so the British sent troops across the water. They expected battle-perhaps another war-but found only the Mandarin. The irate official left too, and the British took the city, though the Chinese never renounced their claim. Missionaries moved in and built churches and schools, pig farmers from the surrounding hills took plots of land within the walls. There was almost no administrative control, and the city became a slum. Yet whenever the Hong Kong government tried to clear it to turn it into a park-evicting the residents in the process-the Chinese government always stepped in. After all, this tiny rectangle of land was still officially their territory.

The situation remained unresolved until the outbreak of World War II. Japanese forces occupied the Kowloon Peninsula and tore down the walls of the city to build a new runway for nearby Kai Tak Airport.

In the aftermath of the war, refugees flooded south to the Kowloon Peninsula. The only trace of the old city was the derelict shell of the Mandarin's house. Yet people gravitated almost instinctively to this rough rectangle of ground. Perhaps it was the feng shui. The Walled City had originally been laid out according to the ancient principles of Chinese philosophy: facing south and overlooking water, with hills and mountains to the north. This ideal alignment, it was said, brought harmony to all citizens. In their desperate plight some refugees may have believed that Kowloon would be a much-needed source of luck and prosperity. Others, however, recalled that this had once been a Chinese enclave in British colonial territory. The stone walls of the "Walled City" had gone, but the refugees were convinced the diplomatic ones remained.

By 1947 there were more than 2,000 squatters camped in Kowloon, their ramshackle huts arranged in almost the exact footprint of the original city. No one wanted to find themselves outside the borders-those on the wrong side of the line risked losing the protection of the Chinese government. The people kept coming, and the camp grew ever more squalid and overcrowded.

Appalled by the conditions, the Hong Kong authorities made plans to clear the refugees. On January 5, 1948, the Public Works Department, supported by a large police presence, removed the squatters and demolished all the slum housing. Within a week, however, the occupiers had returned to rebuild their shacks. When the police attempted to intervene, a riot broke out. News of the disturbances spread across China, and the plight of the "residents" of Kowloon became a cause célèbre. The British consulate in Canton was set on fire, and a group of students in Shanghai staged a protest strike. Officials from the Chinese government traveled to the Walled City-and officially encouraged the refugees to continue the struggle against their British oppressors.

The provincial Canton government sent a delegation on a "comfort mission" to the region, supplementing the distribution of food and medical aid with messages advocating militant action. The Chinese Foreign Ministry continued to argue that they retained jurisdiction over the city and its people. Amid mounting tension, the Hong Kong government relented. The eviction program was halted, and the police withdrew. From a temporary refugee camp, Kowloon now began to evolve into something more permanent. A new city was being founded on the ruins of the old.

What kind of city? Naturally, the judgment of Sir Alexander Grantham, Governor of Hong Kong from 1947 to 1957, was damning. Kowloon, he wrote, had become "a cesspool of iniquity, with heroin divans, brothels and everything unsavoury." The Chinese claims to sovereignty over Kowloon did not extend to any day-to-day administration; they merely used its uncertain status as a convenient tool for political point-scoring. After the disturbances in 1948, the Hong Kong government had settled on a similar policy of non-intervention. The result was a city outside the law: There was no tax, no regulation of businesses, no health or planning systems, no police presence. People could come to Kowloon, and, in official terms, disappear. It was little surprise that criminal activity flourished. Five Triad gangs-the King Yee, Sun Yee On, 14K, Wo Shing Wo, and Tai Ho Choi-took up residence. Kowloon's extralegal status made it the perfect place for the manufacture, sale and use of drugs such as opium and heroin. The city that had been founded to police the traffic of opium became the epicenter of Hong Kong's narcotics trade.

Organized crime may have dominated much of Kowloon, but it did not define the city. Entrepreneurs, attracted by low rents offered by private landlords, saw a unique opportunity. Hundreds of factories were established, with entire families manning the production lines. Conditions were often appalling, yet productivity-and profit-remarkable. Goods made in Kowloon were exported throughout Hong Kong, China, and even, in some cases, the world. Plastics and textile manufacturing were a specialty, as was food production. To the blissful ignorance of Hong Kong's well-heeled residents, the dumplings and fish balls served in their restaurants were frequently sourced from Kowloon.

The citizens of the Walled City demonstrated an extraordinary capacity for change and adaptation. The boundaries of their world were tightly constrained, yet, as more people continued to enter the city, their architecture met the demand. As modern high-rises grew up in Hong Kong, the builders of Kowloon copied what they saw, erecting tower blocks of their own. Thin columns, established on foundations often consisting of thin layers of concrete poured into shallow trenches, started to extend skywards. With no requirement for planning permission, structures were thrown up with amazing speed. Subsidence and settlement were common. Because the high-rises would often lean against each other, residents called them "lovers' buildings."

As the blocks began to merge together, the city became less a collection of buildings and more a single structure, a solid block filled with thousands of individual units designed to meet every requirement of a city: living, working, learning, production, commerce, trade, and leisure. Increasingly, residents were physically sealed off from the outside world. Light did not penetrate down to the narrow lanes leading between the high-rises. It was the beginning of the City of Darkness.

A system of self-government gradually emerged. In 1963, for the first time in over a decade, the Hong Kong authorities attempted to intervene in Kowloon, issuing a demolition order for one corner of the city, and proposing to relocate the displaced residents to a new estate development nearby. When the plans were made public, the community instantly formed a "Kowloon City anti-demolition committee."

At 9:20 am on January 14, 1987, 400 officials from the Hong Kong Housing Department erected cordons around the 83 streets and alleys leading into and out of the Walled City. Then they entered the city on a mission to contact and survey every single resident. Earlier that morning, it had been announced that the city was to be cleared and redeveloped as a public park-just as the Hong Kong Government had intended over half a century before. Except this time, there was to be no Chinese resistance. Two years earlier, on December 19, 1984, the governments of China and Great Britain had signed a joint declaration to transfer sovereignty of Hong Kong back to China on July 1, 1997. The Chinese Foreign Ministry had always used Kowloon as a political pawn to remind the British and the world of their claim over the land granted to Britain in 1898. The 99 years were almost up.

The plans for clearance and demolition were kept secret. Compensation was a key element of the eviction process, so there was the danger of a sudden influx of people looking to take a slice of government money. For six months, the Housing Department kept Kowloon under surveillance to gather evidence of population numbers. The compensation package for residents and business owners totaled $2.76 billion. On average, residents received around $380,000 for their individual flats. Negotiations progressed over several years, and by November 1991, only 457 households were still to agree terms. By that time, most of the 33,000 residents had moved out. Some, however, clung on to the end, and on July 2, 1992, riot police entered the city and forced out the last remaining residents. A tall wire fence was erected to encircle the whole site-following almost exactly the line once marked out by the city's original granite wall.

On March 23, 1993, a wrecker's ball smashed into the side of an eight-story tower block on the edge of the Walled City. This was a solitary, ceremonial swing. The real work of demolishing Kowloon, piece by piece, would begin several weeks later. The moment was applauded by a crowd of invited guests and dignitaries. It was also greeted with shouts of anger from former residents who had gathered for one last, futile protest. It took almost exactly a year to reduce the rest of the city to dust and rubble.

Remarkably, from within the modern wreckage, fragments of the original city emerged. There were two granite plaques, each marked with Chinese characters: One read "South Gate," and the other "Kowloon Walled City." Once the ruins of the tower blocks had been cleared away, developers uncovered segments of the foundations of the original wall, along with three of the iron cannons that had once bristled from the city's ramparts. A solitary building still stood at the center of Kowloon, the one structure to have survived throughout its whole turbulent history-the office of the Mandarin. Over the course of the next year, the ruins began their rapid conversion into a landscaped park, modeled on the famous 17th-century Jiangnan gardens built by the Qing Dynasty.

The paths running through these new gardens were named after the streets and buildings of the demolished slum. The Kowloon Walled City Park was officially opened on December 22, 1995, by the British Governor of Hong Kong, Chris Patten. It had taken some six decades, but at last Kowloon was transformed into the "place of popular resort" envisaged by Sir William Peel, the Governor of Hong Kong in 1934: six-and-a half acres of ornate bamboo pavilions, pretty water features, and vibrant greenery.

This is the story of the rise and fall of a slum. It was born out of a quirk of history, it exploited its unsavory reputation, and, as is the fate of all slums, it became an embarrassment before being leveled by the authorities. Is there any greater significance to its story than that? Many would argue not. But while locals and tourists now enjoy the park, some still crave the claustrophobic darkness. Theorists from the wilder shores of architecture keep returning to the idea of Kowloon. On this tiny rectangle of ground, a single community created something that had only existed before in the avant garde imagination: the "organic megastructure."

The concept of the megastructure emerged in the late 1960s, as a radical departure from the conventional idea of the city. Instead of buildings being arranged around public spaces, streets, and squares, the megastructuralists envisioned one continuous city binding citizens together in a set of modular units, capable of unlimited expansion. It was a city designed to live, evolve, and adapt, fulfilling all the needs of its people, and with the capacity to endlessly "plug in" more units to meet changing desires.

Architects pushed this idea to extremes, most sensationally in the work of Alan Boutwell and Michael Mitchell, who in 1969 proposed a "continuous city for 1,000,000 human beings." They envisaged a single, linear city, sitting on 100-meter-high pillars, running in a straight line between the Atlantic and Pacific coasts of North America. Kowloon, in effect, was proof of concept. Within its anarchist society, argued the megastructuralists, was the kernel of an architectural utopia.

Others, however, saw Kowloon not as a petri dish for urban theory, but as a model or diorama for a new kind of construction-one that did not exist in the ordinary physical plane, yet was as real as anything that could be seen or touched. The renowned American science fiction writer, William Gibson, described Kowloon, not long before its demolition, as a "hive of dream." What Gibson saw in the unregulated, organic chaos of the City of Darkness was an embodiment of his famous concept of "cyberspace"-or, as we would call it today, the internet.

In its formative years, the internet provided the perfect environment for the establishment of multiple, self-regulating communities. Just like the Walled City, it operated outside of law or external oversight. It was post-design and post-government. Thousands, even millions of Kowloons could spring up at will in cyberspace: digital enclaves thriving on creative and political freedom, possessing an autonomous, dynamic structure that allowed them to grow at a frightening, near-exponential rate. It was also, just like the Walled City, living on borrowed time. "I'd always maintained that much of the anarchy and craziness of the early internet had a lot to do with the fact that governments just hadn't realized it was there," commented Gibson. "It was like this territory came into being, and there were no railroads, there were no lawmen, and people were doing whatever they wanted, but I always took it for granted that the railroads would come and there would be law west of Dodge."

Yet to Gibson's mind, the people of Kowloon-and the megastructuralists-were groping toward the next stage in human evolution. He saw the Walled City, that accident of urban birth, as a crude, subconscious schematic of the future, a blueprint for coders and hackers, the architects of the web, to follow. In his 1996 novel Idoru, Gibson imagined a virtual Kowloon, a Walled City 2.0 recreated as an ultra-libertarian web sanctuary: "These people, the ones they say made a hole in the net, they found the data, the history of it. Maps, pictures ... They built it again."

So the wrecking ball may not only have been destroying a notorious slum. Perhaps Kowloon was also the first, true, physical monument to the internet. A city that offered a glimpse into the infinite horizons, structural possibilities-and inherent amorality-of the digital realm.

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Anarchic, organic, surreal, this enclave was once among the most densely populated places on Earth.

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Densely populated land has great potential to better foster communities and give safer spaces to live in, like demonstrated in the neighborhoods of Tokyo

There are many ways to do density, with many not being successful

Tokyo has closeknit ties within its community with children being able to freely play on the street without parental supervision because elders will be watching over

Tokyo also has a superb public transportation system that makes cars less feasible, making the city able to be more dense and more environmentally friendly

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Economy and health

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Social connections within densely populated cities

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Context + Introduction + Focus (Problem Statement)

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Context + Introduction + Focus (Problem Statement)

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(2-3 sources)  SITUATE your investigation of the complexities of the issue.  Present why this issue/problem is worth investigating, and begin to focus this issue within the framework of your specific lens.

Make clear the significance of your lens focus in relation to the broader context/issue.

Many problems like sanitation and safety can all be traced down to how land is used within a city. By exploring innovative and traditional ways to utilize land, a city can better its environmental sustainability and the communities within it

Densely populated cities in the past have two sides to them. They may promise greater economic output, at the expense of greater emissions and disease. Source 2 goes over Kolkata, India's compact city model and concludes that in its case, the model leads to worse living conditions. However, it mentions that with proper implementation, it could work well.

Kowloon City goes to another extreme in sources 5,6. The city grows like a living organism and expands without bounds.

There can be many ways to approach these densely populated cities, but further research will be needed to determine a proper solution in land use

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ways that land use affects the environment