Land Use Change In Africa Research Articles

The Contribution of Transpiration to Precipitation Over African Watersheds.

The redistribution of biological (transpiration) and non-biological (interception loss, soil evaporation) fluxes of terrestrial evaporation via atmospheric circulation and precipitation is an important Earth system process. In vegetated ecosystems, transpiration dominates terrestrial evaporation and is thought to be crucial for regional moisture recycling and ecosystem functioning. However, the spatial and temporal variability in the dependency of precipitation on transpiration remains understudied, particularly in sparsely sampled regions like Africa. Here, we investigate how biological and non-biological sources of evaporation in Africa contribute to rainfall over the major watersheds in the continent. Our study is based on simulated atmospheric moisture trajectories derived from the Lagrangian model FLEXPART, driven by 1° resolution reanalysis data over 1981-2016. Using daily satellite-based fractions of transpiration over terrestrial evaporation, we isolate the contribution of vegetation to monthly rainfall. Furthermore, we highlight two watersheds (Congo and Senegal) for which we explore intra- and interannual variability of different precipitation sources, and where we find contrasting patterns of vegetation-sourced precipitation within and between years. Overall, our results show that almost 50% of the annual rainfall in Africa originates from transpiration, although the variability between watersheds is large (5%-68%). We conclude that, considering the current and projected patterns of land use change in Africa, a better understanding of the implications for continental-scale water availability is needed.

Opportunities for biodiversity conservation outside of Gorongosa National Park, Mozambique: A multispecies approach

Habitat loss and fragmentation threaten wildlife and ecosystems across the globe, especially in multi-use landscapes outside of protected areas, which are ubiquitous. Amid rapid land-use changes in Africa especially, managers need tools to prioritize conservation efforts outside of protected areas. We studied how human activities affect the distribution and composition of a medium-to-large sized mammalian community with various habitat requirements in a sustainable-use forestry concession in central Mozambique. We deployed 75 motion-detecting cameras from June to October 2017, and photographed 30 mammalian species. We used hierarchical, multi-species occupancy models to estimate species richness at each station and compared the relative effects of natural and anthropogenic features on the presence of individual species and groups of species when categorized into taxonomic/functional groups and body size groups. Predicted richness at each station varied from 3 to 17 species, and both human and natural parameters varied in their importance for the occupancy likelihood for different animals. When species were grouped by taxonomies and diets, settlement proximity negatively affected the occupancies of carnivores, insectivores, and other foragers. Similarly, settlement proximity negatively affected the occupancies of species in all body size groups. However, active roads and human activity rates did not have a statistically significant relationship with any species' occupancies or detection rates, respectively. Overall, mammalian richness was highest far from human settlements in the concession and close to rivers. Building on scant knowledge of wildlife communities across mosaics of different land uses, our results shed light on understudied species assemblages to guide conservation efforts in Mozambique.

Influence of urbanization-driven land use/cover change on climate: The case of Addis Ababa, Ethiopia

Land use change is the second most important anthropogenic influence on climate beside the emission of greenhouse gases. Urbanization is leading to significant land use changes in Africa since the continent is undergoing rapid urbanization and population growth in recent decades. Addis Ababa is one of these fast growing cities in the continent. Therefore, detection of land use change is very important to identify its impact on climate and sustainable land use management of the city. The study used Landsat images to generate land use/land cover change map for the city. The normalized difference vegetation index (NDVI) is used to detect the major changes of vegetation cover occurred between 1986 and 2011 as a result of land use and land cover change. Downscaled HadCM3 simulations under A2 and B2 emission scenarios is used to investigate future urban heat island (UHI) over the city of Addis Ababa. In the city, the analysis of Landsat images has shown that the built-up areas have increased by 121.88 km2 within the last 25 years. This finding is consistent with NDVI images taken over the same period that reveal a decline in vegetation cover. The impact of the urbanization-driven land use/cover change has resulted in notable nocturnal urban heat island (UHI) as revealed from an average increase in minimum temperature of 1.5°C at the centre of the city relative to rural site over the 1960–2001 period. The mean of the 2006–2010 spatial minimum temperature anomaly with respect to the base period mean of 1981–2005 is consistent with the observed UHI. The temperature in the central areas (both commercial and residential sectors) of Addis Ababa is warmer than the surrounding areas. The thermal gradient increase from about 1.44°C at the centre (Arada, Addis Ketema, Lideta and Kirkos) to 0.21°C at the peripheral parts of the city (Gulele, Bole, Nefasilk-Lafto, Kolfe Keranio and east of Yeka sub-cities) transecting across the hot (high-density urban) to moderately warm to cool (non-built-up) areas. However, the maximum temperature and rainfall exhibit variability that follows topographic differences. Future urban climate change projections of urban heat island formation under A2 and B2 emission scenarios show that the nocturnal UHI will be intense in winter or dry season episodes in the city. The highest urban warming is from October to December (2.5°C to 3.2°C) during 2050s and 2080s.

A full greenhouse gases budget of Africa: synthesis, uncertainties, and vulnerabilities

Abstract. This paper, developed under the framework of the RECCAP initiative, aims at providing improved estimates of the carbon and GHG (CO2, CH4 and N2O) balance of continental Africa. The various components and processes of the African carbon and GHG budget are considered, existing data reviewed, and new data from different methodologies (inventories, ecosystem flux measurements, models, and atmospheric inversions) presented. Uncertainties are quantified and current gaps and weaknesses in knowledge and monitoring systems described in order to guide future requirements. The majority of results agree that Africa is a small sink of carbon on an annual scale, with an average value of −0.61 ± 0.58 Pg C yr−1. Nevertheless, the emissions of CH4 and N2O may turn Africa into a net source of radiative forcing in CO2 equivalent terms. At sub-regional level, there is significant spatial variability in both sources and sinks, due to the diversity of biomes represented and differences in the degree of anthropic impacts. Southern Africa is the main source region; while central Africa, with its evergreen tropical forests, is the main sink. Emissions from land-use change in Africa are significant (around 0.32 ± 0.05 Pg C yr−1), even higher than the fossil fuel emissions: this is a unique feature among all the continents. There could be significant carbon losses from forest land even without deforestation, resulting from the impact of selective logging. Fires play a significant role in the African carbon cycle, with 1.03 ± 0.22 Pg C yr−1 of carbon emissions, and 90% originating in savannas and dry woodlands. A large portion of the wild fire emissions are compensated by CO2 uptake during the growing season, but an uncertain fraction of the emission from wood harvested for domestic use is not. Most of these fluxes have large interannual variability, on the order of ±0.5 Pg C yr−1 in standard deviation, accounting for around 25% of the year-to-year variation in the global carbon budget. Despite the high uncertainty, the estimates provided in this paper show the important role that Africa plays in the global carbon cycle, both in terms of absolute contribution, and as a key source of interannual variability.

Evaluation of an integrated land use change model including a scenario analysis of land use change for continental Africa

The global integrated land use model, LandSHIFT, is evaluated by testing its performance against available data sets, by analyzing the sensitivity of model parameters and structure, and by conducting a scenario analysis of future land use change in Africa. Despite the paucity of suitable data sets, a range of different tests were designed to make best use of available data and to examine the model’s ability to compute cropland suitability, extent of cropland area, and location of deforestation. The model showed more ability to calculate the spatial distribution of cropland suitability and continental average deforestation rates than to compute the spatial distribution of deforestation. LandSHIFT was found to be particularly sensitive to assumptions about future climate change for simulations extending over several decades through the influence of climate on cropland and grassland productivity. With regards to the scenario analysis, the model was applied to two scenarios for Africa that cover a wide range of assumptions about future driving forces. Results showed that cropland land may expand greatly up to 2050 (34–40%, depending on the scenario) because of increasing food demand and despite expected increases in crop yield. This expansion comes largely at the expense of forested land, although the average continental deforestation rate computed from 2000 to 2050 is lower than the computed rate for the 1990s. The testing and scenario analysis showed the ability of the model to develop consistent scenarios of land use change on the continental scale by combining the effects of driving forces and competition between land uses in a single spatially-explicit framework.

Managing forests, livestock, and crops under global warming: a micro‐econometric analysis of land use changes in Africa*

This paper examines potential land use changes in Africa under climate change by building an integrated model of crop management, animal husbandry, and forestry. Using micro‐level decisions from around 9000 household surveys in 11 countries, we analyze the choice of land types across the landscape with a multinomial discrete choice model. The choices and future adaptation measures are analyzed as a mosaic based on the typology of Agro‐Ecological Zones. The results indicate that if climate becomes hotter and drier, Africa will adapt by increasing a joint production of crops and animals, especially in the lowland savannahs. On the other hand, if climate becomes wetter, it will switch more to forests, either with crops or with both crops and livestock, especially in the mid and high elevation humid zones. Forestry will play a significant role in adaptation when a substantial increase in precipitation makes animal husbandry an unattractive alternative.

Scenarios of agricultural land-use change in Africa under changing climate conditions

Scenarios of agricultural land-use change in Africa under changing climate conditions

Scenarios of agricultural land-use change in Africa under changing climate conditions

This article was submitted without an abstract, please refer to the full-text PDF file.