land use change and migrant birds in the sahel: research brief 4
Drivers of
Land Use
Change and
Migrant
Birds in the
Sahel
• Land use change in the Sahel is likely to be important factor in
the decline of European-African migrant birds, although the
links between birds and people are not well understood.
• Land use change is the result of the decisions of landholders
trying to make a living. Their decisions are the result of a wide
range of social and economic processes that are not uniform
in space and in time.
• A chain of causation goes from macro-scale processes
such as the world economy, through immediate drivers on
landowners, to the actual decisions they make about how to
manage their land, to impact on the ground. These change
habitats and directly impact birds.
• It is important that the complexity of the drivers of land use
change are recognized, or attempts to influence land use to
protect bird habitat will be ineffective and perhaps cause
harm.
• More research is needed into the links between people and
birds in the Sahel
Introduction
The countries of the Sahel, south of the Sahara desert, are
amongst the poorest in the world1. The annual rainfall is
2-600mm, falling on a single short season. Farmers and
pastoralists in the Sahel adopt diverse livelihoods to cope
with variability of rainfall within and between years2.
The farmlands, grasslands and woodlands of the Sahel are
important for a wide variety of birds that migrate from
Europe after breeding3. Many of these Eurasian-African
bird migrants are declining in Europe4. These declines
are not well understood, but potential causes including
changes on breeding grounds, flyways and wintering
grounds. Environmental change in the Sahel is widely
believed to be an important factor. Rainfall variability is a
key driver of environmental change. Another is likely to be
anthropogenic land cover change associated with changing
economies in Sahelian countries. Our understanding of the
drivers of present and future land use change in the Sahel
for Afro-Palearctic migrant birds is limited.
West Africa and the Sahel
While in the Sahel, migrant birds use landscapes actively
managed by farmers and livestock keepers. Important
bird habitats in the Sahel are shaped by human land use,
changing in response to the livelihood needs of landholders
and increasing demands for food and other commodities,
as well as by human-forced climate change.
West Africa is a region of rapid social and economic change.
Its population rose from 70 to 318 million from 1950 to
2010, and is projected to double by 2050 to 650 million.
Urban population increased from 7 million in 1950 to
140 million in 2010. Population and urban growth have
important implications for food security, regional markets
and household incomes5.
Studies of birds in the Sahel tend to define land cover terms
of habitat type6. However, as in Europe, most land in the
Sahel is owned, occupied and intensively managed by
people. The form of land use and the detailed way in which
it is managed profoundly shape the extent and quality of
habitat available for migrant birds.
The most extensive rural land uses in the Sahel are
agriculture and livestock grazing (many households do
both, some specialise in livestock, sometimes practicing
long-distance movements). Trees and woodland are
important resources (particularly fuelwood).
Farm,
grassland, shrub and wooded environments are the most
important for land bird migrants in the Sahel7.
Table 1 - Categories in Land use Change Networks
Macro-scale
drivers
Multiple macro-scale drivers of social and economic change in Sahelian countries include: governance (the decisions governments make about economic and
social development policy), drought and rainfall variability and agricultural commodity prices. These all influenced by the state of the world economy and political economy. These macro-scale causations are common to all forms of land use.
Immediate
drivers
Macro-scale factors in turn influence more immediate drivers of land use decisions by the owners and occupiers of land in the Sahel, such as: increase in urban
wealth, increases in urban population, increase in rural population, increase in wealth of rural households, increased rural-urban migration, increase in urban
wealth and economic activity.
Land use
decisions
These drivers in turn influence land use decisions. These include: increased cash cropping, increased mechanization, increased use of farm labour and increased
demand for non-food crops.
Impacts
Land use decisions lead to particular impacts directly relevant to field, grassland or woodland habitats of importance to migrant birds. These include increased
cutting of trees and shrubs, increased planting of trees and shrubs, increased creation of new fields, shorter fallow cycles, more or less weeding of farms.
Habitat
Responses
These actions in turn influence habitats important for birds: creation or clearance of closed woodland, reduced woodland tree density, increase or decrease of
woody scrub, increase or decrease of trees and scrub on formerly open land, increase or decrease of structural and floristic diversity on open land.
land use change and migrant birds in the sahel: research brief 4
of factors associated with the loss of trees and scrub
from open land in the Sahel through selected changes in
agriculture and grazing.
Conclusions
Ecological studies of migrants in the Sahel tend not to
analyse how land is being managed, or by whom. Sahel
migrant bird decline is often attributed to environmental
degradation as a result of climate variability, and
unsustainable land use associated with human population
increases9. This interpretation draws on a stereotyped
‘desertification narrative’10, and ignores the phenomenon
of local ‘greening’ of the Sahel11.
However, land use change in Sahelian countries is the result
of a complex set of drivers that vary in both in space and
time. The intrinsic variability in Sahelian rainfall (and new
uncertainties about anthropogenic climate change due to
CO2) present serious challenges to local people and bird
conservationists, and growing food demand from cities
and rural areas present difficult policy challenges.
Figure 1: Partial Network of Factors of Tree Decline
Land Use in the Sahel
Land use is the result of a interaction of a wide range of
social and economic processes. These are highly variable
in both space (between counties, and between ecological
regions within countries) and in time (as economic and
other drivers change). They also vary with the ethnic
identity of landholders, and in response to many aspects of
social cultural and political factors. The land use decisions
of farmers or livestock-keepers are never the direct result
of single driving forces (for example levels of population
growth or poverty in West Africa), but reflect the outworking
of numerous factors at every scale from the individual
through the household and community to the region,
country and globe. This makes the exercise of identifying
the drivers of land use change in the Sahel difficult.
Networks of Causation
Understanding of the drivers of land use change must start
with the decisions of Sahelian land users and the factors
that influence them. Those influences can be thought of
as notional chains within wider networks of causation.
Using the principles of the ‘PSIR’ (Pressure-State-ImpactResult) framework, a series of categories can be identified
that go from macro-scale processes such as the world
economy, through immediate drivers on landowners, to
the actual decisions they make about how to manage their
land (Table 1). In turn these impact on habitats, and drive
changes in habitat amount or character. It is these habitat
changes that directly impact birds8.
The Complexity of Land Use Change
An illustration of the complex drivers of land use change is
show in Figure 1, which shows a small part of the network
Political and economic factors such as the rural impacts
of urban wealth and demand and the growth of the
regional consumption economy are powerful drivers of
land use change. The importance of such factors is likely to
increase in future, for example with the policy emphasis on
increasing the productivity of Sahelian land for food and
biofuels.
The Sahel includes Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Sudan,
Ethiopia and Eritrea. About 50 million people live in the Sahel
2
Raynaut, C. (1998) Societies and Nature in the Sahel, Routledge, London.
3
Hahn, S., Bauer, S. & Liechti, F. (2009) ‘The natural link between Europe and Africa: 2.1
billion birds on migration’ Oikos, 118 624-626.
4
Hewson, C.M. & Noble, D.G. (2009) ‘Population trends of breeding birds in British woodlands over a 32-year period: relationships with food, habitat and migratory behaviour’,
Ibis 151: 464-486; Zwarts, L., Bijlsma, R.G., Kamp, J. van der, Wymenga, E. (2009) Living
on the edge: Wetlands and birds in a changing Sahel. KNNV Publishing.
5
West African Futures, Club du Sahel et de l’Afrique de l’Ouest (Clubhttp://www.oecd.
org/pages/0,3417,en_38233741_38246608_1_1_1_1_1,00.html)
6
Land Use Change and Migrant Birds in the Sahel (2011) Research Brief 2, Key Habitats
for Declining Migrant Birds in the West African Sahel.
7
Land Use Change and Migrant Birds in the Sahel (2011) Research Brief 3, Migrant Birds
and Environmental Change in the Sahel.
8
Research Brief 3, see note 7
9
Wilson, J.M. & Cresswell, W. (2006) ‘How robust are Palearctic migrants to habitat loss
and degradation in the Sahel?’ Ibis 148: 789-800; Cresswell, W.R.L. et al. (2007) ‘Changes
in densities of Sahelian bird species in response to recent habitat degradation’. Ostrich
78: 247-253.
10
Ribot, J. (1999) ‘A history of fear: imagining deforestation in the West African dryland
forests’, Global Ecology and Biogeography 8: 291-300; Mortimore, M.J. (1998) Roots in
the African Dust: sustaining the subSaharan drylands, Cambridge University Press, Cambridge.
11
Olson, L., Eklundh, L., and Ardo, J. (2005) ‘A recent greening of the Sahel: trends, patterns and potential causes, Journal of Arid Environments 63: 556-66.
1
These Research Briefs are an output of the project ‘Reversing the declines of African-Palaearctic migrants: understanding the
social and economic factors driving land use change in sub-Saharan West African wintering areas’, funded by the CCI Fund and
the Newton Trust. Project partners were the British Trust for Ornithology, the Royal Society for the Protection of Birds, and the
Departments of Geography and Zoology, University of Cambridge. http://www.geog.cam.ac.uk/research/projects/landusemigrantbirds/