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The Great Green Wall in the Sahel  

Cheikh Mbow

For several decades, the Sahelian countries have been facing continuing rainfall shortages, which, coupled with anthropogenic factors, have severely disrupted the great ecological balance, leading the area in an inexorable process of desertification and land degradation. The Sahel faces a persistent problem of climate change with high rainfall variability and frequent droughts, and this is one of the major drivers of population’s vulnerability in the region. Communities struggle against severe land degradation processes and live in an unprecedented loss of productivity that hampers their livelihoods and puts them among the populations in the world that are the most vulnerable to climatic change. In response to severe land degradation, 11 countries of the Sahel agreed to work together to address the policy, investment, and institutional barriers to establishing a land-restoration program that addresses climate change and land degradation. The program is called the Pan-Africa Initiative for the Great Green Wall (GGW). The initiative aims at helping to halt desertification and land degradation in the Sahelian zone, improving the lives and livelihoods of smallholder farmers and pastoralists in the area and helping its populations to develop effective adaptation strategies and responses through the use of tree-based development programs. To make the GGW initiative successful, member countries have established a coordinated and integrated effort from the government level to local scales and engaged with many stakeholders. Planning, decision-making, and actions on the ground is guided by participation and engagement, informed by policy-relevant knowledge to address the set of scalable land-restoration practices, and address drivers of land use change in various human-environmental contexts. In many countries, activities specific to achieving the GGW objectives have been initiated in the last five years.


Climate Change Adaptation  

Philipp Schmidt-Thomé

Climate change adaptation is the ability of a society or a natural system to adjust to the (changing) conditions that support life in a certain climate region, including weather extremes in that region. The current discussion on climate change adaptation began in the 1990s, with the publication of the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Since the beginning of the 21st century, most countries, and many regions and municipalities have started to develop and implement climate change adaptation strategies and plans. But since the implementation of adaptation measures must be planned and conducted at the local level, a major challenge is to actually implement adaptation to climate change in practice. One challenge is that scientific results are mainly published on international or national levels, and political guidelines are written at transnational (e.g., European Union), national, or regional levels—these scientific results must be downscaled, interpreted, and adapted to local municipal or community levels. Needless to say, the challenges for implementation are also rooted in a large number of uncertainties, from long time spans to matters of scale, as well as in economic, political, and social interests. From a human perspective, climate change impacts occur rather slowly, while local decision makers are engaged with daily business over much shorter time spans. Among the obstacles to implementing adaptation measures to climate change are three major groups of uncertainties: (a) the uncertainties surrounding the development of our future climate, which include the exact climate sensitivity of anthropogenic greenhouse gas emissions, the reliability of emission scenarios and underlying storylines, and inherent uncertainties in climate models; (b) uncertainties about anthropogenically induced climate change impacts (e.g., long-term sea level changes, changing weather patterns, and extreme events); and (c) uncertainties about the future development of socioeconomic and political structures as well as legislative frameworks. Besides slow changes, such as changing sea levels and vegetation zones, extreme events (natural hazards) are a factor of major importance. Many societies and their socioeconomic systems are not properly adapted to their current climate zones (e.g., intensive agriculture in dry zones) or to extreme events (e.g., housing built in flood-prone areas). Adaptation measures can be successful only by gaining common societal agreement on their necessity and overall benefit. Ideally, climate change adaptation measures are combined with disaster risk reduction measures to enhance resilience on short, medium, and long time scales. The role of uncertainties and time horizons is addressed by developing climate change adaptation measures on community level and in close cooperation with local actors and stakeholders, focusing on strengthening resilience by addressing current and emerging vulnerability patterns. Successful adaptation measures are usually achieved by developing “no-regret” measures, in other words—measures that have at least one function of immediate social and/or economic benefit as well as long-term, future benefits. To identify socially acceptable and financially viable adaptation measures successfully, it is useful to employ participatory tools that give all involved parties and decision makers the possibility to engage in the process of identifying adaptation measures that best fit collective needs.


Agricultural Subsidies and the Environment  

Heather Williams

Worldwide, governments subsidize agriculture at the rate of approximately 1 billion dollars per day. This figure rises to about twice that when export and biofuels production subsidies and state financing for dams and river basin engineering are included. These policies guide land use in numerous ways, including growers’ choices of crop and buyers’ demand for commodities. The three types of state subsidies that shape land use and the environment are land settlement programs, price and income supports, and energy and emissions initiatives. Together these subsidies have created perennial surpluses in global stores of cereal grains, cotton, and dairy, with production increases outstripping population growth. Subsidies to land settlement, to crop prices, and to processing and refining of cereals and fiber, therefore, can be shown to have independent and largely deleterious effect on soil fertility, fresh water supplies, biodiversity, and atmospheric carbon.


An Image Reconnaissance: Agricultural Patterns and Related Environmental Impacts Viewed From Space  

Richard W. Hazlett and Joshua Peck

Satellite reconnaissance of the Earth’s surface provides critical information about the state of human interaction with the natural environment. The strongest impact is agricultural, reflecting land-use approaches to food production extending back to the dawn of civilization. To variable degrees, depending upon location, regional field patterns result from traditional farming practices, surveying methods, regional histories, policies, political agendas, environmental circumstances, and economic welfare. Satellite imaging in photographic true or false color is an important means of evaluating the nature and implications of agricultural practices and their impacts on the surrounding world. Important platforms with publicly accessible links to satellite image sets include those of the European Space Agency, U.S. National Aeronautics and Space Administration, the Centre D’etudes Spatiales, Airbus, and various other governmental programs. Reprocessing of data worldwide in scope by commercial concerns including Digital Globe, Terrametrics, and GoogleEarth in the 21st century enable ready examination of most of the Earth’s surface in great detail and natural colors. The potential for monitoring and improving understanding of agriculture and its role in the Earth system is considerable thanks to these new ways of viewing the planet. Space reconnaissance starkly reveals the consequences of unique land surveys for the rapid development of agriculture and political control in wilderness areas, including the U.S. Public Land Survey and Tierras Bajas systems. Traditional approaches toward agriculture are clearly shown in ribbon farms, English enclosures and medieval field systems, and terracing in many parts of the world. Irrigation works, some thousands of years old, may be seen in floodplains and dryland areas, notably the Maghreb and the deep Sahara, where center-pivot fields have recently appeared in areas once considered too dry to cultivate. Approaches for controlling erosion, including buffer zones, shelter belts, strip and contour farming, can be easily identified. Also evident are features related to field erosion and soil alteration that have advanced to crisis stage, such as badland development and widespread salinization. Pollution related to farm runoff, and the piecemeal (if not rapid) loss of farmlands due to urbanization can be examined in ways favoring more comprehensive evaluation of human impacts on the planetary surface. Developments in space technologies and observational platforms will continue indefinitely, promising ever-increasing capacity to understand how humans relate to the environment.


Terrestrial Processes and Their Roles in Climate Change  

Nathalie de Noblet-Ducoudré and Andrew J. Pitman

The land surface is where humans live and where they source their water and food. The land surface plays an important role in climate and anthropogenic climate change both as a driver of change and as a system that responds to change. Soils and vegetation influence the exchanges of water, energy and carbon between the land and the overlying atmosphere and thus contribute to the variability and the evolution of climate. But the role of the land in climate is scale dependent which means different processes matter on different timescales and over different spatial scales. Climate change alters the functioning of the land with changes in the seasonal cycle of ecosystem growth, in the extent of forests, the melt of permafrost, the magnitude and frequency of disturbances such as fire, drought, … Those changes feedback into climate at both the global and the regional scales. In addition, humans perturb the land conditions via deforestation, irrigation, urbanization, … and this directly affects climatic conditions at the local to regional scales with also sometimes global consequences via the release of greenhouse gases. Not accounting for land surface processes in climate modelling, whatever the spatial scale, will result in biases in the climate simulations.


Impact of Land–Atmosphere Interactions on Sahel Climate  

Yongkang Xue

The Sahel of Africa has been identified as having the strongest land–atmosphere (L/A) interactions on Earth. The Sahelian L/A interaction studies started in the late 1970s. However, due to controversies surrounding the early studies, in which only a single land parameter was considered in L/A interactions, the credibility of land-surface effects on the Sahel’s climate has long been challenged. Using general circulation models and regional climate models coupled with biogeophysical and dynamic vegetation models as well as applying analyses of satellite-derived data, field measurements, and assimilation data, the effects of land-surface processes on West African monsoon variability, which dominates the Sahel climate system at intraseasonal, seasonal, interannual, and decadal scales, as well as mesoscale, have been extensively investigated to realistically explore the Sahel L/A interaction: its effects and the mechanisms involved. The Sahel suffered the longest and most severe drought on the planet in the 20th century. The devastating environmental and socioeconomic consequences resulting from drought-induced famines in the Sahel have provided strong motivation for the scientific community and society to understand the causes of the drought and its impact. It was controversial and under debate whether the drought was a natural process, mainly induced by sea-surface temperature variability, or was affected by anthropogenic activities. Diagnostic and modeling studies of the sea-surface temperature have consistently demonstrated it exerts great influence on the Sahel climate system, but sea-surface temperature is unable to explain the full scope of the Sahel climate variability and the later 20th century’s drought. The effect of land-surface processes, especially land-cover and land-use change, on the drought have also been extensively investigated. The results with more realistic land-surface models suggest land processes are a first-order contributor to the Sahel climate and to its drought during the later 1960s to the 1980s, comparable to sea surface temperature effects. The issues that caused controversies in the early studies have been properly addressed in the studies with state-of-the-art models and available data. The mechanisms through which land processes affect the atmosphere are also elucidated in a number of studies. Land-surface processes not only affect vertical transfer of radiative fluxes and heat fluxes but also affect horizontal advections through their effect on the atmospheric heating rate and moisture flux convergence/divergence as well as horizontal temperature gradients.


Urban Sprawl and the Control of Land Use  

Alex Anas

Urban sprawl in popular sources is vaguely defined and largely misunderstood, having acquired a pejorative meaning. Economists should ask whether particular patterns of urban land use are an outcome of an efficient allocation of resources. Theoretical economic modeling has been used to show that more not less, sprawl often improves economic efficiency. More sprawl can cause a reduction in traffic congestion. Job suburbanization can generally increase sprawl but improves economic efficiency. Limiting sprawl in some cities by direct control of the land use can increase sprawl in other cities, and aggregate sprawl in all cities combined can increase. That urban population growth causes more urban sprawl is verified by empirically implemented general equilibrium models, but—contrary to common belief—the increase in travel times that accompanies such sprawl are very modest. Urban growth boundaries to limit urban sprawl cause large deadweight losses by raising land prices and should be seen to be socially intolerable but often are not. It is good policy to use corrective taxation for negative externalities such as traffic congestion and to implement property tax reforms to reduce or eliminate distortive taxation. Under various circumstances such fiscal measures improve welfare by increasing urban sprawl. The flight of the rich from American central cities, large lot zoning in the suburbs, and the financing of schools by property tax revenues are seen as causes of sprawl. There is also evidence that more heterogeneity among consumers and more unequal income distributions cause more urban sprawl. The connections between agglomeration economies and urban sprawl are less clear. The emerging technology of autonomous vehicles can have major implications for the future of urban spatial structure and is likely to add to sprawl.


Social Equity, Land Use Planning, and Flood Mitigation  

Malini Roy and Philip Berke

Every flood event reveals hidden disparities within cities—disparities in capacities to anticipate, respond to, and recover from disasters. Studies examining drivers of disparity have found that highly socially vulnerable (e.g., poor, minority) neighborhoods sustain more damage, have access to fewer recovery resources, and experience slower recovery. Climate change and unregulated growth are likely to exacerbate these disparities. Scholars argue that disparities along the lines of race and income are partly due to inadequate planning. Planning for flood mitigation has lacked a deep understanding of values and has therefore overlooked needs and exacerbated physical vulnerability in socially vulnerable neighborhoods. Increasing local and international attention to the socioeconomic drivers of disaster impacts elicits the question: How can land use planning foster more equitable hazard mitigation practices that meet the needs identified by marginalized communities? Equitable hazard mitigation is advanced through three dimensions. First, contextual equity involves preparing an information base that asks who is vulnerable to flooding, who has (not) been engaged in planning decisions that affect vulnerability to flooding, and why. Recognizing contextual inequities in plans is the first step to making visible historic discrimination and addressing drivers of persisting political disenfranchisement. Second, procedural equity involves organizing a participation process that critically considers whom participation processes should target, how stakeholders should be inclusively engaged, and how multiple values should inform policy priorities. Dedicated planning-participation processes can repair past legacies of power information imbalances and co-produce planning goals. A process where vulnerable, marginalized citizens have as much information and as much say in policy decisions as others adds nuance to planners’ understanding of needs, and enables the incorporation of overlooked values into distribution of land use policies. Third, distributional equity involves designing planning policies so that flood mitigation services and infrastructure are directed to neighborhoods and households most in need. Moreover, distributional equity considerations need to be integrated across the local government plans (e.g., transportation plan, housing plan, and hazard mitigation plan) that affect growth in hazardous areas. Social equity outcomes further rely on the degree of knowledge transfer between the three dimensions. The effectiveness of distributional equity is critically dependent on contextual and procedural equity and affects how plan outcomes align with the needs and values of disadvantaged and vulnerable communities. Likewise, the scope of contextual equity is shaped by historical distributional and procedural equity or lack thereof. To advance equitable outcomes, more research is required on the implementation and effectiveness of different land use planning approaches. Future inquiries should examine social equity through a multihazard lens; empirically analyze the causal relationships among the contextual, procedural, and distributional equity; and explore the effectiveness of different planning tools and governance structures in fostering socially equitable hazard mitigation.


Road Building in Brazil  

Emily Story

For much of its history, Brazil’s population remained bound along the coastline. Geographic features, such as coastal mountain ranges and a relative lack of navigable rivers, stymied efforts to settle and exploit the vast interior. Because of its inaccessibility to authorities based on the coast, the interior became a place of refuge for Indigenous communities and runaway slaves. During the colonial period (1500–1822) and several decades beyond, waterways and Indigenous footpaths (sometimes widened to allow for ox carts and mule trains) were the main routes for travel into the hinterland. Slavers and mineral prospectors known as bandeirantes founded scattered settlements in Minas Gerais, Goiás, and Mato Grosso. As the Industrial Revolution created new demands and technological possibilities in the late 19th century, efforts to connect the interior to the coast came via the telegraph and railroad. The rubber boom of that era precipitated greater settlement of the Amazon region and relied on riverine transport. Road building has intensified since the mid-20th century. The new capital, Brasília, centerpiece of President Juscelino Kubitschek’s (1956–1961) campaign to achieve “Fifty Years of Progress,” initiated a new network of highways, later expanded by the military regime (1964–1985). Those efforts aimed to promote economic development, redirect internal migration, and extend the territorial control of the central government. Migrants and entrepreneurs, traveling on official highways and illegal roads constructed along the way, set fire to grasslands and forests to convert them into pasture. Roads, both legal and illegal, thus opened the way for transformations of the ecosystems of the Brazilian interior. At the same time, they created conditions for intensified conflict between newcomers and those who had long called the interior home.


Deforestation: Drivers, Implications, and Policy Responses  

Christiane W. Runyan and Jeff Stehm

Over the last 8,000 years, cumulative forest loss amounted to approximately 2.2 billion hectares, reducing forest cover from about 47% of Earth’s land surface to roughly 30% in 2015. These losses mostly occurred in tropical forests (58%), followed by boreal (27%) and temperate forests (8%). The rate of loss has slowed from 7.3 Mha/year between 1990–2000 to 3.3 Mha/year between 2010–2015. Globally since the 1980s, the net loss in the tropics has been outweighed by a net gain in the subtropical, temperate, and boreal climate zones. Deforestation is driven by a number of complex direct and indirect factors. Agricultural expansion (both commercial and subsistence) is the primary driver, followed by mining, infrastructure extension, and urban expansion. In turn, population and economic growth drive the demand for agricultural, mining, and timber products as well as supporting infrastructure. Population growth and changing consumer preferences, for instance, will increase global food demand 50% by 2050, possibly requiring a net increase of approximately 70 million ha of arable land under cultivation. This increase is unlikely to be offset entirely by agricultural intensification due to limits on yield increases and land quality. Deforestation is also affected by other factors such as land tenure uncertainties, poor governance, low capacity of public forestry agencies, and inadequate planning and monitoring. Forest loss has a number of environmental, economic, and social implications. Forests provide an expansive range of environmental benefits across local, regional, and global scales, including: hydrological benefits (e.g., regulating water supply and river discharge), climate benefits (e.g., precipitation recycling, regulating local and global temperature, and carbon sequestration), biogeochemical benefits (e.g., enhancing nutrient availability and reducing nutrient losses), biodiversity benefits, and the support of ecosystem stability and resiliency. The long-term loss of forest resources also negatively affects societies and economies. The forest sector in 2011 contributed roughly 0.9% of global GDP or USD 600 billion. About 850 million people globally live in forest ecosystems, with an estimated 350 million people entirely dependent on forest ecosystems for their livelihoods. Understanding how to best manage remaining forest resources in order to preserve their unique qualities will be a challenge that requires an integrated set of policy responses. Developing and implementing effective policies will require a better understanding of the socio-ecological dynamics of forests, a more accurate and timely ability to measure and monitor forest resources, sound methodologies to assess the effectiveness of policies, and more efficacious methodologies for valuing trade-offs between competing objectives.


changing landscapes, human impact on  

John Bintliff

The Classical world witnessed many forms of physical landscape change due to long-term and short-term geological and climatological processes. There have also been alterations to the land surface resulting from an interaction between human impact and these natural factors. Cyclical changes in land use, agricultural technology, economy, and politics have continually transformed the rural landscapes of the Mediterranean and the wider Classical world and their mapping, in turn, can shed light on fundamental aspects of ancient society that are not always documented in Classical texts.

As with natural causes of landscape change (see changing landscapes, natural causes of), a useful approach is offered by the chronological framework developed by French historian Fernand Braudel, who envisaged the Mediterranean past as created through the interaction of dynamic forces operating in parallel but on different wavelengths of time: the long term (up to as much as thousands or millions of years, not at all in the awareness of past human agents); the medium term (centuries or more, not clearly cognisant to contemporaries); and the short term (observable within a human lifetime or less).


Deforestation of the Brazilian Amazon  

Phillip Fearnside

Deforestation in Brazilian Amazonia destroys environmental services that are important for the whole world, and especially for Brazil itself. These services include maintaining biodiversity, avoiding global warming, and recycling water that provides rainfall to Amazonia, to other parts of Brazil, such as São Paulo, and to neighboring countries, such as Argentina. The forest also maintains the human populations and cultures that depend on it. Deforestation rates have gone up and down over the years with major economic cycles. A peak of 27,772 km2/year was reached in 2004, followed by a major decline to 4571 km2/year in 2012, after which the rate trended upward, reaching 7989 km2/year in 2016 (equivalent to about 1.5 hectares per minute). Most (70%) of the decline occurred by 2007, and the slowing in this period is almost entirely explained by declining prices of export commodities such as soy and beef. Government repression measures explain the continued decline from 2008 to 2012, but an important part of the effect of the repression program hinges on a fragile base: a 2008 decision that makes the absence of pending fines a prerequisite for obtaining credit for agriculture and ranching. This could be reversed at the stroke of a pen, and this is a priority for the powerful “ruralist” voting bloc in the National Congress. Massive plans for highways, dams, and other infrastructure in Amazonia, if carried out, will add to forces in the direction of increased deforestation. Deforestation occurs for a wide variety of reasons that vary in different historical periods, in different locations, and in different phases of the process at any given location. Economic cycles, such as recessions and the ups and downs of commodity markets, are one influence. The traditional economic logic, where people deforest to make a profit by producing products from agriculture and ranching, is important but only a part of the story. Ulterior motives also drive deforestation. Land speculation is critical in many circumstances, where the increase in land values (bid up, for example, as a safe haven to protect money from hyperinflation) can yield much higher returns than anything produced by the land. Even without the hyperinflation that came under control in 1994, highway projects can yield speculative fortunes to those who are lucky or shrewd enough to have holdings along the highway route. The practical way to secure land holdings is to deforest for cattle pasture. This is also critical to obtaining and defending legal title to the land. In the past, it has also been the key to large ranches gaining generous fiscal incentives from the government. Money laundering also makes deforestation attractive, allowing funds from drug trafficking, tax evasion, and corruption to be converted to “legal” money. Deforestation receives impulses from logging, mining, and, especially, road construction. Soybeans and cattle ranching are the main replacements for forest, and recently expanded export markets are giving strength to these drivers. Population growth and household dynamics are important for areas dominated by small farmers. Extreme degradation, where tree mortality from logging and successive droughts and forest fires replace forest with open nonforest vegetation, is increasing as a kind of deforestation, and is likely to increase much more in the future. Controlling deforestation requires addressing its multiple causes. Repression through fines and other command-and-control measures is essential to avoid a presumption of impunity, but these controls must be part of a broader program that addresses underlying causes. The many forms of government subsidies for deforestation must be removed or redirected, and the various ulterior motives must be combated. Industry agreements restricting commodity purchases from properties with illegal deforestation (or from areas cleared after a specified cutoff) have a place in efforts to contain forest loss, despite some problems. A “soy moratorium” has been in effect since 2006, and a “cattle agreement” since 2009. Creation and defense of protected areas is an important part of deforestation control, including both indigenous lands and a variety of kinds of “conservation units.” Containing infrastructure projects is essential if deforestation is to be held in check: once roads are built, much of what happens is outside the government’s control. The notion that the 2005–2012 deforestation slowdown means that the process is under control and that infrastructure projects can be built at will is extremely dangerous. One must also abandon myths that divert efforts to contain deforestation; these include “sustainable logging” and the use of “green” funds for expensive programs to reforest degraded lands rather than retain areas of remaining natural forests. Finally, one must provide alternatives to support the rural population of small farmers. Large investors, on the other hand, can fend for themselves. Tapping the value of the environmental services of the forest has been proposed as an alternative basis for sustaining both the rural population and the forest. Despite some progress, a variety of challenges remain. One thing is clear: most of Brazil’s Amazonian deforestation is not “development.” Trading the forest for a vast expanse of extensive cattle pasture does little to secure the well-being of the region’s rural population, is not sustainable, and sacrifices Amazonia’s most valuable resources.


Environmental Impacts of Tropical Soybean and Palm Oil Crops  

Kimberly M. Carlson and Rachael D. Garrett

Oil crops play a critical role in global food and energy systems. Since these crops have high oil content, they provide cooking oils for human consumption, biofuels for energy, feed for animals, and ingredients in beauty products and industrial processes. In 2014, oil crops occupied about 20% of crop harvested area worldwide. While small-scale oil crop production for subsistence or local consumption continues in certain regions, global demand for these versatile crops has led to substantial expansion of oil crop agriculture destined for export or urban markets. This expansion and subsequent cultivation has diverse effects on the environment, including loss of forests, savannas, and grasslands, greenhouse gas emissions, regional climate change, biodiversity decline, fire, and altered water quality and hydrology. Oil palm in Southeast Asia and soybean in South America have been identified as major proximate causes of tropical deforestation and environmental degradation. Stringent conservation policies and yield increases are thought to be critical to reducing rates of soybean and oil palm expansion into natural ecosystems. However, the higher profits that often accompany greater yields may encourage further expansion, while policies that restrict oil crop expansion in one region may generate secondary “spillover” effects on other crops and regions. Due to these complex feedbacks, ensuring a sustainable supply of oil crop products to meet global demand remains a major challenge for agricultural companies, farmers, governments, and civil society.


Urban Heat Islands and Their Associated Impacts on Health  

Clare Heaviside

Towns and cities generally exhibit higher temperatures than rural areas for a number of reasons, including the effect that urban materials have on the natural balance of incoming and outgoing energy at the surface level, the shape and geometry of buildings, and the impact of anthropogenic heating. This localized heating means that towns and cities are often described as urban heat islands (UHIs). Urbanized areas modify local temperatures, but also other meteorological variables such as wind speed and direction and rainfall patterns. The magnitude of the UHI for a given town or city tends to scale with the size of population, although smaller towns of just thousands of inhabitants can have an appreciable UHI effect. The UHI “intensity” (the difference in temperature between a city center and a rural reference point outside the city) is on the order of a few degrees Celsius on average, but can peak at as much as 10°C in larger cities, given the right conditions. UHIs tend to be enhanced during heatwaves, when there is lots of sunshine and a lack of wind to provide ventilation and disperse the warm air. The UHI is most pronounced at night, when rural areas tend to be cooler than cities and urban materials radiate the energy they have stored during the day into the local atmosphere. As well as affecting local weather patterns and interacting with local air pollution, the UHI can directly affect health through heat exposure, which can exacerbate minor illnesses, affect occupational performance, or increase the risk of hospitalization and even death. Urban populations can face serious risks to health during heatwaves whereby the heat associated with the UHI contributes additional warming. Heat-related health risks are likely to increase in future against a background of climate change and increasing urbanization throughout much of the world. However, there are ways to reduce urban temperatures and avoid some of the health impacts of the UHI through behavioral changes, modification of buildings, or by urban scale interventions. It is important to understand the physical properties of the UHI and its impact on health to evaluate the potential for interventions to reduce heat-related impacts.


Changes in Land Use Influenced by Anthropogenic Activity  

Lang Wang and Zong-Liang Yang

The terms “land cover” and “land use” are often used interchangeably, although they have different meanings. Land cover is the biophysical material at the surface of the Earth, whereas land use refers to how people use the land surface. Land use concerns the resources of the land, their products, and benefits, in addition to land management actions and activities. The history of changes in land use has passed through several major stages driven by developments in science and technology and demands for food, fiber, energy, and shelter. Modern changes in land use have been increasingly affected by anthropogenic activities at a scale and magnitude that have not been seen. These changes in land use are largely driven by population growth, urban expansion, increasing demands for energy and food, changes in diets and lifestyles, and changing socioeconomic conditions. About 70% of the Earth’s ice-free land surface has been altered by changes in land use, and these changes have had environmental impacts worldwide, ranging from effects on the composition of the Earth’s atmosphere and climate to the extensive modification of terrestrial ecosystems, habitats, and biodiversity. A number of different methods have been developed give a thorough understanding of these changes in land use and the multiple effects and feedbacks involved. Earth system observations and models are examples of two crucial technologies, although there are considerable uncertainties in both techniques. Cross-disciplinary collaborations are highly desirable in future studies of land use and management. The goals of mitigating climate change and maintaining sustainability should always be considered before implementing any new land management strategies.


The Economics of Tropical Rainforest Preservation  

Carlos Eduardo Frickmann Young

Tropical forests are among the most biodiverse areas on Earth. They contribute to ecosystem functions, including regulating water flow and maintaining one of the most important carbon sinks on the planet, and provide resources for important economic activities, such as timber and nontimber products and fish and other food. Rainforests are not empty of human population and are sites of ethnically and culturally diverse cultures that are responsible for many human languages and dialects. They also provide resources for important economic activities, such as timber and nontimber products. However, tropical deforestation caused by the expansion of agricultural activities and unsustainable logging continues at very high levels. The causes of forest loss vary by region. Livestock is the main driver in the Amazon, but commercial plantations (soybeans, sugar cane, and other tradable crops) also have an impact on deforestation, in many cases associated with violent conflicts over land tenure. In Southeast Asia, logging motivated by the tropical timber trade plays an important role, although palm oil plantations are an increasing cause of deforestation. In Africa, large-scale agricultural and industrial activities are less important, and the most critical factor is the expansion of subsistence and small-scale agriculture. However, trade-oriented activities, such as cocoa and coffee plantations in West Africa and logging in Central Africa, are becoming increasingly important. Public policies have a strong influence on these changes in land use, from traditional community-based livelihood practices to for-profit livestock, cultivation, and timber extraction. Investments in infrastructure, tax and credit incentives, and institutional structures to stimulate migration and deforestation represent economic incentives that lead to deforestation. Poor governance and a lack of resources and political will to protect the traditional rights of the population and environmental resources are another cause of the continuous reduction of tropical forests. Consequently, deforestation prevents the expansion of economic activities that could be established without threats to the remnants of native forest. There are also negative social consequences for the local population, which suffers from the degradation of the natural resources on which their production is based, and is hampered by air pollution caused by forest fires. In some situations, a vicious cycle is created between poverty and deforestation, since the expansion of the agricultural frontier reduces the forest areas where traditional communities once operated, but without generating job opportunities. New approaches are required to reverse this paradigm and to lay the foundation for a sustainable economy based on the provision of ecosystem services provided by tropical forests. These include (a) better governance and public management capacity, (b) incentives for economic activities compatible with the preservation of the tropical forest, and (c) large-scale adoption of economic instruments to support biodiversity and ecosystem services. Public policies are necessary to correct market failures and incorporate the values of ecosystem services in the land use decision process. In addition to penalties for predatory actions, incentives are needed for activities that support forest preservation, so the forest is worth retaining rather than clearing. Improving governance capacity, combining advanced science and technology with traditional knowledge, and improving the management of existing activities can also help to ensure sustainable development in tropical forest regions.


Housing Policy and Affordable Housing  

Christian A.L. Hilber and Olivier Schöni

Lack of affordable housing is a growing and often primary policy concern in cities throughout the world. The main underlying cause for the “affordability crisis,” which has been mounting for decades, is a combination of strong and growing demand for housing in desirable areas in conjunction with tight long-term supply constraints—both physical and man-made regulatory ones. The affordability crisis tends to predominately affect low- and moderate-income households. Increasingly, however, middle-income households—which do not usually qualify for government support—are similarly affected. Policies that aim to tackle the housing affordability issue are numerous and differ enormously across countries. Key policies include mortgage subsidies, government equity loans, rent control, social or public housing, housing vouchers, low-income tax credits, and inclusionary zoning, among others. The overarching aim of these policies is to (a) reduce the periodic housing costs of or (b) improve access to a certain tenure mode for qualifying households. Existing evidence reveals that the effectiveness and the distributional and social welfare effects of housing policies depend not only on policy design but also on local market conditions, institutional settings, indirect (dis)incentives, and general equilibrium adjustments. Although many mainstream housing policies are ineffective, cost-inefficient, and/or have undesirable distributional effects from an equity standpoint, they tend to be politically popular. This is partly because targeted households poorly understand adverse indirect effects, which is exploited by vote-seeking politicians. Partly, it is because often the true beneficiaries of the policies are the politically powerful existing property owners (homeowners and landlords), who are not targeted but nevertheless benefit from positive policy-induced house price and rent capitalization effects. The facts that existing homeowners often have a voter majority and landlords additionally may be able to influence the political process via lobbying lead to the conundrum of ineffective yet politically popular housing policies. In addition to targeted policies for individuals most in need (e.g., via housing vouchers or by providing subsidized housing), the most effective policies to improve housing affordability in superstar cities for all income groups might be those that focus on the root causes of the problem. These are (a) the strongly and unequally growing demand for housing in desirable markets and (b) tight land use restrictions imposed by a majority of existing property owners that limit total supply of housing in these markets. Designing policies that tackle the root causes of the affordability crisis and help those in need, yet are palatable to a voter majority, is a major challenge for benevolent policymakers.


Disease, Ecology, and the Environment in Colonial Mexico  

Bradley Skopyk and Elinor G. K. Melville

The onset of Spanish imperial rule in Mexico in 1521 had profound consequences well beyond the political and cultural spheres. It also altered Mexico’s environment, reconstituting the region’s ecology as new fauna, flora, and microorganisms were added and as the population dynamics of native Mexican biota fluctuated in response to Old World arrivals. While the consequences of myriad interactions between native and non-native species were vast and complex, it was the decimation of indigenous persons by pathogens that was one of the first biological consequences of colonization (in fact, occurring first in 1520, one year before the fall of the Aztec state) and one of the most important. Mexican human populations were reduced by 80 to 90 percent, effecting cascading ecological consequences across the physical and biological geography of Mexico. Forests regenerated, terraced slopes degraded, and much of the Mexican landscape lost its anthropogenic aspect. Simultaneously, ungulate introductions transformed Mexican flora and likely initiated soil erosion in some regions that, when transported to fluvial environments, disrupted the flow of rivers. On the other hand, pigs, sheep, goats, horses, and other ungulates altered plant communities through selective seed dispersion. New economic pursuits such as brick making and silver mining increased demand for heat energy that, in an unprecedented manner, encouraged intensive forest usage and, probably, regional deforestation, although empirical data on historical forest cover are still lacking. Severe climate variability, of a scale not experienced for at least five hundred years and perhaps many millennia, occurred simultaneously with colonial-induced ecological change. A significant conquest-era drought was followed by one of the coolest and wettest periods of the Holocene; a strong pluvial in the Mexican context lasted from 1540 to around 1620. Subsequent anomalies of both temperature (cold) and precipitation (either wet or dry) occurred in the 1640s and 1650s, and from the 1690s until about 1705. Together, these climate anomalies are known as the core Little Ice Age, and initiated agrarian transitions, hazardous flooding, prolonged droughts, epidemics, epizootics, and recurring agrarian crises that destabilized human health and spurred high rates of mortality. Soil degradation and suppressed forest cover are also likely outcomes of this process. Although debate abounds regarding the timing, extent, and causes of soil and water degradation, there is little doubt that extensive degradation occurred and destabilized late-colonial and early-Republic societies.


Religious Regulation in the United States  

Barbara A. McGraw and James T. Richardson

Although the United States Constitution presumably was designed to avoid “regulation” of religion, there is an interplay between religious individuals and private organizations, on the one hand, and the state, on the other hand, which has a regulatory effect on religion in some areas of public life. The First Amendment’s “Religious Clauses” prohibit an establishment of religion and preserve the right to free exercise of religion. An important area of contention and development in legislation and Supreme Court jurisprudence involves free exercise accommodations or exemptions to laws and rules that generally apply to everyone. These are particularly at issue in the workplace, in correctional institutions, and in the military. The latter two give rise to establishment issues, which have been resolved in favor of free exercise, as government support of religion has been held to be necessary to preserve the free exercise rights of inmates and service personnel. The enactment of the Religious Freedom Restoration Act (RFRA) and the Religious Land Use and Institutionalized Persons Act (RLUIPA) have led to a much greater deference to religious rights, resulting in accommodations that would not have been required under preexisting legislation and judicial interpretation. Another such area involves religious organizations themselves, in particular issues regarding tax-exempt status, land use, and faith-based initiatives. A provision in the tax code known as the Johnson Amendment, which restrains religious (and other tax-exempt organizations) from certain political activities, has been challenged recently as a limitation on free speech, however without success so far. Issues involving local government limitations on religious organizations’ land use through zoning restrictions are now being addressed more favorably for religious organizations through the land-use provisions of RLUIPA, although not without controversy. Faith-based initiatives have promoted religious organizations, or faith-based organizations (FBOs), as important government partners, which are eligible to receive public funds for the delivery of social services. Since the late 20th century, there has been a gradual, but significant shift toward greater respect for individuals’ and groups’ religious rights, especially reflected in recent legislation and Supreme Court decisions. Such trends suggest that, although religion has come into conflict with legal-policy developments in other areas, such as those involving gay marriage and contraception coverage, the right to practice one’s religion and participate in public endeavors alongside nonreligious individuals and groups, is likely to continue to expand for the foreseeable future.


Space and Church–State Controversies in America  

John C. Blakeman

Issues of church and state are an important element of American religious history and politics. Church–state issues frequently concern the extent of government regulation over religious groups and individuals, and they address fundamental issues, from the constitutional limits on government regulation of religiously inspired conduct to state and local government zoning of religious congregations and property owned and used by religious groups. Space is often a part of church–state issues. Beginning with early debates over religious liberty in the Puritan colonies in the 1600s, and again during the American Revolution and framing of the U.S. Constitution between 1775 and 1790, spatial conceptions of the proper role between church and state, and between government and religion, are prominent. Two fundamental thinkers on American religious liberty, the Puritan minister Roger Williams and the constitutional framer James Madison, illustrate this dimension of church–state relations. Disputes over space, church, and state are often resolved by the court system through litigation, or through the political process. Such disputes often stem from government policies and regulations that affect how a congregation or religious group uses its own property. For instance, zoning and other municipal ordinances may affect and burden how a religious group uses its property and even interfere with a group’s religious mission. Religious beliefs may compel a congregation to use its property to engage in charitable works, yet it may be prohibited from doing so due to government regulations on how its property can be used. Or when a congregation seeks to expand its facilities to attract more members, or even build a new worship center elsewhere, it may encounter government policies that regulate its ability to do so. Other disputes over space arise when government regulation of public property affects a religious group’s use of it. For example, some religious groups stake a sacred claim to land or other space owned by the government. However, government regulations concerning how the land is used might interfere with a group’s ability to act upon its sacred beliefs. In some cases, religious groups may seek to use public property for religious purposes and activities, such as the display of a religious symbol or for proselytizing to the public, and government policies may prevent that in order to avoid violating the Constitution’s ban on government establishment of religion in the First Amendment. A final view of space and church–state issues is more conceptual and less grounded in tangible space, land, and property. Some religious groups seek a more abstract, intangible space between them and government regulation. Groups such as the Old Order Amish that seek to separate from the world will erect a buffer space between themselves and government regulation, so as to preserve the purity, and sanctity, of their way of life that is inextricably linked to their specific religious beliefs.