INVESTING IN TREES AND LANDSCAPE ... - PROFOR

It then outlines a set of criteria, evaluation processes, and data sources to identify landscapes with
suitable biophysical conditions for investment in landscape restoration.
Farming and Land Use Systems
Geographic variation across Africa and diverse historical patterns of production and trade have
led to a rich variety of land use and farming systems. Systems based on commercial tree crops
are found in the lowlands of western Africa (including with rice) and the highlands of eastern
Africa; pastoral and agropastoral systems in the drylands; and forest-based systems in central Africa.
Systems based on grains and root crops dominate elsewhere. The area of Africa covered by farming
systems predominantly based on trees and other perennials is relatively significant: 11 percent is
covered by forest-based systems, in which producers rely on forestry/tree products interspersed
with annual crop production. Another 3 percent is in tree crop systems (e.g., cocoa and oil palm); 1
percent is in mixed rice-tree systems; and another 1 percent is in highland perennials (e.g., coffee
and tea) (Dixon and Gullivar 2001). In each type of farming system, landscape degradation takes a
somewhat different form, as do priorities and mechanisms for restoration.
Scale and Consequences of Land and Forest Degradation
Although it is now somewhat out of date, the United Nations Food and Agriculture Organization’s
(FAO’s) 2000 Global Assessment of Soil Degradation (GLASOD) provided one of the most
comprehensive assessments of global land degradation. Overall, 4.2 percent of Africa has strongly
or extremely degraded soils—the highest percentage of any continent and twice the world average
of 2.1 percent. Pockets of strong or extreme soil degradation are clustered so that certain landscapes
have a high degree of degradation across a high percentage of mapping units. These severely and
very severely degraded landscapes comprise about 6 million km 2 of Sub-Saharan Africa (about onefourth
of the region’s land), of which 2 million km 2 have been degraded as the result of agricultural
activities. These areas are concentrated at the southern margin of the Sahara Desert (stretching from
the Atlantic Ocean to the Red Sea), South Africa, Madagascar, around Lake Victoria, and in pockets
in coastal West Africa. The primary causes of degradation are deforestation, overgrazing (particularly
in dryland regions), and overexploitation of vegetation for domestic use, including biomass energy.
In Sub-Saharan Africa, land degradation is closely correlated with population density (FAO 2000).
A recent geospatial analysis of tree cover in productive areas (Zomer et al. 2009) compares current
levels of tree cover with potential tree cover, defined on the basis of geographic region, climate, and
population density. This analysis suggests that several regions in Africa are below their potential in
terms of tree cover (and corresponding livelihood benefits and ecosystem services) and could be
priority regions for investment in restoration. These areas are in the West African coastal lowlands,
pockets in northern and southern Nigeria, the eastern coast of Madagascar, north central Ethiopia,
a band south of the Sahara, the area from central Tanzania to the Kenya/Uganda border and into
southern Sudan, and the northern part of South Africa. Of course, these generalized patterns are
mediated at the landscape level by biophysical, socioeconomic, market, and policy factors.
Recently, Vlek and colleagues (2011) used a time series of satellite imagery (1982–2003) to assess
changes in net primary productivity (NPP) in Africa. NPP integrates multiple causal factors (e.g., soil
fertility, water availability, degradation from human activity) and has multiple implications for human
well-being (e.g., availability of biomass as crops, livestock fodder, or forest resources, as well as levels
of ecosystem functions such as water purification and carbon sequestration). Although the changes
50 INVESTING IN TREES AND LANDSCAPE RESTORATION IN AFRICA