Knowledge for better food systems

Estimating the Environmental Costs of Africa’s Massive “Development Corridors”

In this paper, researchers from James Cook University, Australia, assess the impact on the environment and agriculture of 33 planned or existing “development corridors” in sub-Saharan Africa. Development corridors are tracts of land earmarked for large-scale infrastructure expansions (e.g. road access) with the aim of increasing agricultural production.

The researchers overlaid a 50-km-wide onto each development corridor and estimated – using the distribution of electric lights visible at night in satellite images – the human occupancy of this area (i.e. the population living in the vicinity of each development corridor; the authors acknowledge that this necessarily excludes communities without electricity). The environmental value of each development corridor band was estimated as a composite index of environmental values, which account for, for example, species diversity, habitat values and carbon storage capacity. Each corridor was then assigned a conservation priority – i.e. an indication of how valuable that corridor was to preserve rather than develop. For example: a corridor with high conservation priority was deemed to be one that had high environmental values and low human occupancy. The researchers also investigated the number of protected areas that would be affected by the corridors. Finally, they estimated the potential agricultural benefits of each development corridor.

The key findings were:

  • The percentage of each development corridor area that was occupied by people varied widely between corridors (ranging from 0.7% to 45.7% of the total area of each corridor band), but most corridors were only very sparsely populated (only 8 of the 33 corridors had visible electric lights in more than 10% of the imaged area).
  • The environmental values of the corridors sampled varied widely, but the environmental value of corridors dominated by forests were significantly higher than of those dominated by savannah woodlands of desert shrublands.
  •  Forest- and savannah-woodland-dominated corridors had significantly higher conservation value than desert shrublands, with the highest conservation values to be found in equatorial corridors of densely forested areas.
  • The main transport links at the centre of the 33 development corridors would bisect a total of 408 protected areas. Including the 50 km wide band around each corridor, 2,169 protected areas fall at least partially within at least one corridor band.
  • While there was great variation in agricultural potential across the corridors examined, the 14 planned corridors were shown to have a lower agricultural potential than the 19 existing ones

Based on these findings the authors conclude that many of the existing or planned corridors (especially the latter) may bring benefits to only very small numbers of people, that these agricultural benefits may be insignificant and that their environmental and conservation costs may be extremely high, going so far as to recommend that a number of these projects ought to be cancelled or at least reined in. The authors note the links between some development corridors and large-scale mining projects and the financial and social ramifications of this; the positive correlation between corridor length and negative environmental impact; and that corridors near areas of existing disruption and impact, e.g. urban areas, will have less negative impact than those in more remote areas. The authors conclude that while development corridors are likely to play an important role in Africa’s development, concerted efforts are needed to ensure that these maximise agricultural gains while minimising environmental harm.


In sub-Saharan Africa, dozens of major "development corridors" have been proposed or are being created to increase agricultural production, mineral exports, and economic integration. The corridors involve large-scale expansion of infrastructure such as roads, railroads, pipelines, and port facilities and will open up extensive areas of land to new environmental pressures. We assessed the potential environmental impacts of 33 planned or existing corridors that, if completed, would total over 53,000 km in length and crisscross much of the African continent. We mapped each corridor and estimated human occupancy (using the distribution of persistent night-lights) and environmental values (endangered and endemic vertebrates, plant diversity, critical habitats, carbon storage, and climate-regulation services) inside a 50-km-wide band overlaid onto each corridor. We also assessed the potential for each corridor to facilitate increases in agricultural production. The corridors varied considerably in their environmental values, and many were only sparsely populated. Because of marginal soils or climates, some corridors appear to have only modest agricultural potential. Collectively, the corridors would bisect over 400 existing protected areas and could degrade a further ~1,800 by promoting habitat disruption near or inside the reserves. We conclude that many of the development corridors will promote serious and largely irreversible environmental changes and should proceed only if rigorous mitigation and protection measures can be employed. Some planned corridors with high environmental values and limited agricultural benefits should possibly be cancelled altogether.


Laurance, W.F., Sloan, S., Weng, L., and Sayer, J.A. (2015) Estimating the Environmental Costs of Africa’s Massive “Development Corridors”. Current Biology 25 (24), 3202–3208

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The 54 countries in Africa – from the dry northern African nations, through those in deserts and rainforests, all the way to the temperate parts of South Africa – are hugely varied in their ethnic, cultural, climatic, geographic, and economic aspects. The continent’s population of over a billion inhabitants, with a median age of 19.7 years, is the youngest in the world. Due to both its localised epidemics of hunger and its huge untapped agricultural potential, Sub-Saharan Africa specifically is a key focus area for many NGOs and development agencies interested in food production and security.

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