Shlomo Angel

Mapping urban areas on a global scale: which of the eight maps now available is more accurate?

Eight groups from government and academia have created 10 global maps that offer a ca 2000 portrait of land in urban use. Our initial investigation found that their estimates of the total amount of urban land differ by as much as an order of magnitude (0.27–3.52 ×106 km2). Since it is not possible for these heterogeneous maps to all represent urban areas accurately, we undertake the first global accuracy assessment of these maps using a two-tiered approach that draws on a stratified random sample of 10 000 high-resolution Google Earth validation sites and 140 medium-resolution Landsat-based city maps. Employing a wide range of accuracy measures at different spatial scales, we conclude that the new MODIS 500 m resolution global urban map has the highest accuracy, followed by a thresholded version of the Global Impervious Surface Area map based on the Night-time Lights and LandScan datasets.

The fragmentation of urban landscapes: global evidence of a key attribute of the spatial structure of cities, 1990–2000

The fragmentation of urban landscapes – or the inter-penetration of the built-up areas of cities and the open spaces in and around them – is a key attribute of their spatial structure. Analyzing satellite images for 1990 and 2000 for a global sample of 120 cities, we find that cities typically contain or disturb vast quantities of open spaces equal in area, on average, to their built-up areas. We also find that fragmentation, defined as the relative share of open space in the urban landscape, is now in decline. Using multiple regression models, we find that larger cities are less fragmented, that higher-income cities are more fragmented, that cities with higher levels of car ownership are less fragmented, and that cities that constrain urban development are less fragmented. We recommend that making room for urban expansion in rapidly growing cities should take into account their expected fragmentation levels.

Preparing for urban expansion: A proposed strategy for intermediate cities in ecuador

Introduction * Part I: Urban Transitions * The Demography of the Urban Transition: What We Know and Don t Know * Urbanization, Poverty and Inequity: Is Rural-Urban Migration a Poverty Problem, or Part of the Solution? * Demographic and Urban Transitions in a Global System and Policy Responses * Part II: Shelter and Urban Poverty * Land and Services for the Urban Poor in Rapidly Urbanizing Countries * Informality and Poverty in Latin American Urban Policies * Preparing for Urban Expansion: A Proposed Strategy for Intermediate Cities in Ecuador * Organizations of the Urban Poor and Equitable Urban Development: Process and Product * Part III: The Social and Sustainable Use of Space * Urban Sustainability and Global Environmental Change: Reflections for an Urban Agenda * Risks of Climate Change for Urban Settlements in Low Elevation Coastal Zones * Urbanization and Ecosystems: Current Patterns and Future Implications * Urban Sprawl: A Challenge for Sustainability * Part IV: The Changing Face of Urban Demography and its Challenges * Notes on Urban-Rural Poverty Projections and the Role of Migration * Women s Empowerment and Gender Equality in Urban Settings: New Vulnerabilities and Opportunities * Young People in an Urban World * Urbanization and Ageing in Developing Countries * Confronting Urbanization and the AIDS Epidemic: A Double-Edged Sword * Providing Information for Social Progress in Urban Areas * Part V: Regional Patterns of Urbanization and Linkages to Development * African Urbanization: Recent Trends and Implications * Socioeconomic Heterogeneity in Urban India * The Urban Transition in China: Trends, Consequences and Policy Implications * Urbanization in Latin America and the Caribbean: Experiences and Lessons Learned * Index

A new plan for African cities: The Ethiopia Urban Expansion Initiative:

Recent research indicates that a simplified approach to urban planning in Sub-Saharan African cities can address the challenges of rapid urban growth. Current plans focus too heavily on the existing area of the city and offer unrealistic agendas for future urban growth, such as densification, containment and high-rise development; plans that are often too complicated and too costly to be deployed in a developing-world context. In response, New York University and the Government of Ethiopia have created a programme to deploy a simple methodology called Making Room for Urban Expansion in 18 Ethiopian cities that are experiencing rapid growth. The programme is called the Ethiopia Urban Expansion Initiative. The Initiative set aside a number of standard planning objectives and instead focused only on expanding city boundaries to include adequate land for expansion, designing and protecting a network of arterial roads spaced approximately 1 km apart, and identifying and protecting environmentally sensitive open spaces. These efforts focused on areas that had not yet been occupied by development. This article reports on the preliminary results from the four Ethiopian cities participating in the Initiative that began in 2013. The results from the first four participating cities show that simple plans can lead to the creation of new arterial roads, increasing access to peripheral land and potentially bringing the available land supply in line with projected growth. These activities can be done at the local level and implemented with limited support from consultants and from the regional and national government, and it requires minimal public investment.