Modeling direct above-ground carbon loss due to urban expansion in Zanzibar City Region, Tanzania

The global urban population is expected to grow by 2.5 billion over the next three decades, and 90% of this growth will occur in African and Asian countries. Urban expansion in these regions is often characterised by ‘informal urbanization’ whereby households self-build without planning permission in contexts of ambiguous, insecure or disputed property rights. Despite the scale of informal urbanization, it has received little attention from scholars working in the domains of urban analytics and city science. Towards addressing this gap, we introduce TI-City, an urban growth model designed to predict the locations, legal status and socio-economic status of future residential developments in an African city. In a bottom-up approach, we use agent-based and cellular automata modelling techniques to predict the geospatial behaviour of key urban development actors, including households, real estate developers and government. We apply the model to the city-region of Accra, Ghana, drawing on local data collection, including a household survey, to parameterise the model. Using a multi-spatial-scale validation technique, we compare TI-City’s ability to simulate historically observed built-up patterns with SLEUTH, a highly popular urban growth model. Results show that TI-City outperforms SLEUTH at each scale, suggesting the model could offer a valuable decision support tool in similar city contexts.

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Mapping the morphology of sprawl and blight: A note on entropy

GeoScape ◽

10.2478/geosc-2021-0001 ◽

2021 ◽

Vol 15 (1) ◽

pp. 1-18

Author(s):

Reza Banai ◽

Anzhelika Antipova ◽

Ehsan Momeni

Keyword(s):

Land Use ◽

Land Cover ◽

Urban Expansion ◽

Entropy Change ◽

Metropolitan Region ◽

List Type ◽

Block Group ◽

City Region ◽

City Center ◽

The City

Abstract The urban expansion from the city center to the suburb and beyond is indicated by Shannon entropy, a robust and versatile measure of sprawl. However, the metropolitan regionwide entropy masks the morphology of land cover and land use consequential to urban expansion within the city-region. To surmount the limitation, we focus on the block-group, which is a US census defined socio-spatial unit that identifies the metropolitan region’s development pattern structurally, forming tracts that comprise neighborhoods. The concentration and dispersion of land use and land cover by block-group reveals a North American metropolitan region’s commonly known but rarely measured spatial structure of its urban and suburban sprawl. We use parcel data from county assessor of property (GIS) and land cover pixel data from the National Land Cover Data (NLCD) to compute block-group land-use and land-cover entropy. The change in block group entropy over a decade indicates whether the city- region’s land use and land cover transition to a concentrated or dispersed pattern. Furthermore, we test a hypothesis that blight correlates with sprawl. Blight and sprawl are among the key factors that plague the metropolitan region. We determine the correlations with household income as well as (block group) distance from the city center. It turns out, blight is among the universally held distance-decay phenomena. The share of the block group’s blighted properties decays (nonlinearly) with distance from the city center. Highlights for public administration, management and planning: • The metropolitan region’s outward growth is highlighted by mapping the changing morphology of the block group within the city-region. • The block group entropy is computed with land use (parcel) and land cover (pixel) data. • The block group entropy change indicates the pattern of the land use and land cover transition with concentration or dispersion. • We test the hypothesis that blight correlates with sprawl with statistical models. • The block group’s blighted properties decrease (nonlinearly) with distance from the city center.

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Impact of Urban Expansion On Carbon Storage Under Multi-Scenario Simulations In Wuhan, China

10.21203/rs.3.rs-1129892/v1 ◽

2021 ◽

Author(s):

Zhuo Wang ◽

Jie Zeng ◽

Wanxu Chen

Keyword(s):

Land Use ◽

Carbon Storage ◽

Anthropogenic Impacts ◽

Urban Expansion ◽

Well Being ◽

Total Carbon ◽

Baseline Scenario ◽

Carbon Loss ◽

Trade Offs ◽

The Impact

Abstract Carbon storage in terrestrial ecosystems, which is the basis of the global carbon cycle, reflects the changes in the environment due to anthropogenic impacts. Rapid and effective assessment of the impact of urban expansion on carbon reserves is vital for the sustainable development of urban ecosystems. Previous studies lack research regarding different scenarios during future city and comprehensive analysis on the driving factors from the socioeconomic point of view. Therefore, this study examined Wuhan, China and explored the latent effects of urban expansion on terrestrial carbon storage by combining the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) and Patch-generating Land Use Simulation (PLUS) model. Based on different socioeconomic strategies, we developed three future scenarios, including Baseline Scenario (BS), Cropland Protection Scenario (CP), and Ecological protection Scenario (EP), to predict the urban built-up land use change from 2015 to 2035 in Wuhan and discussed the carbon storage impacts of urban expansion. The result shows that: (1) Wuhan's urban built-up land area expanded 2.67 times between 1980 and 2015, which is approximately 685.17 km2 and is expected to continuously expand to 1,349–1,945.01 km2 by 2035. (2) Urban expansion in Wuhan has caused carbon storage loss by 5.12×106 t during 1980–2015 and will lead to carbon storage loss by 6.15×106 t, 4.7×106 t, and 4.05×106 t under BS, CP, and EP scenarios from 2015 to 2035, accounting for 85.42%, 81.74%, and 78.79% of the total carbon loss, respectively. (3) The occupation of cropland by urban expansion is closely related to the road system expansion, which is the main driver of carbon storage reduction from 2015 to 2035. (4) We expect that by 2035, the districts facing carbon loss caused by the growth of urban built-up land will expand outward around secondary roads, and the scale of outward expansion under various scenarios will be ranked as: BS >CP > EP. In combination, the InVEST and the PLUS model can assess the impact of urban expansion on carbon storage more efficiently and is conducive to carrying out urban planning and promoting a dynamic balance between urban economic development and human well-being.

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Ancient and current resilience in the Chengdu Plain: Agropolitan development re-‘revisited’

Urban Studies ◽

10.1177/0042098019843020 ◽

2019 ◽

Vol 57 (7) ◽

pp. 1372-1397 ◽

Cited By ~ 1

Author(s):

Daniel B Abramson

Keyword(s):

Forest Cover ◽

Agricultural Landscape ◽

Landscape Heterogeneity ◽

Irrigation System ◽

Urban Expansion ◽

Flood Management ◽

Ecological Resilience ◽

City Region ◽

Chengdu Plain ◽

Landscape Preservation

The Dujiangyan irrigation system, China’s largest, is one of the world’s most important examples of sustainable agropolitan development, maintained by a relatively decentralised system of governance that minimises bureaucratic oversight and depends on significant local autonomy at many scales down to the household. At its historic core in the Chengdu Plain, the system has supported over 2000 years of near-continuously stable urban culture, as well as some of the world’s highest sustained long-term per-hectare productivity and diversity of grain and other crops, especially considering its high population density, forest cover, general biodiversity and flood management success. During the past decade, rapid urban expansion has turned the Chengdu Plain from a net grain exporter into a grain importer, and has radically transformed its productive functioning and distinctive scattered settlement pattern, reorganising much of the landscape into larger, corporately-managed farms, and more concentrated and infrastructure-intensive settlements of non-farming as well as farming households. Community-scale case studies of spatial-morphological and household socio-economic variants on the regional trend help to articulate what is at stake. Neither market-driven ‘laissez-faire’ rural development nor local state-driven spatial settlement consolidation and corporatisation of production seem to correlate well with important factors of resilience: landscape heterogeneity; crop diversity and food production; permaculture; and flexibility in household independence and choice of livelihood. Management of the irrigation system should be linked to community-based agricultural landscape preservation and productive dwelling, as sources of adaptive capacity crucial to the social-ecological resilience of the city-region, the nation and perhaps all humanity.

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