Climate change, health and disease in the forests of Africa

Prof. James Fairhead, Sussex Univrsity, UK

Jones et al 2008 (Nature)

• ‘wildlife host species richness’ is a significant predictor for the emergence of zoonotic Emerging Infectious Diseases with a wildlife origin.’

• ‘Zoonoses from wildlife represent the most significant, growing threat to global health of all EIDs’

• ‘Efforts to conserve areas rich in wildlife diversity by reducing anthropic activity may have added value in reducing the likelihood of future zoonotic disease emergence’

Map of the geographic origins of EID events 1940-2004 (Jones 2008)

Global distribution of relative risk of EID event caused by zoonotic pathogens from

wildlife (Jones 2008)

Jones (2008)

• ‘Efforts to conserve areas rich in wildlife diversity by reducing anthropic activity may have added value in reducing the likelihood of future zoonotic disease emergence

‘Potential forest of West Africa’

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Original Forest CoverAbout half of the forest that was present under modern (i.e. post-Pleistocene) climatic conditions, and before the spread of human influence, has disappeared (see map below), largely through the impact of man's activities. The spread of agriculture and animal husbandry, the harvesting of forests for timber and fuel, and the expansion of populated areas have all taken their toll on forests. The causes and timing of forest loss differ between regions and forest types, as do the current trends in change in forest cover.

Original forest is that estimated to have covered the planet about 8,000 years ago, before large-scale disturbance by modern society began.

Copy1987 World Resources Institute. All rights reserved. Updated foreright © st maps available at Global Forest Watch

‘Original’ high forest zone of West Africa

Schematic transect of Original Climax Vegetation (top) and Current vegetation

(bottom), from the wet South to dry North

Fairhead and Leach field site in Republic of Guinea

Forest ‘Islands’ (red) in Savanna (blue) seen by satellite

Compare 1989 and 1952

Analysis of rest of West Africa

Deforestation exaggeration in Sierra Leone

• “As much as 5,000,000 ha may still have featured little disturbed forest as recently as the end of World War II. It is a measure of the pervasive impact of human activities that the amount of primary moist forest now believed to remain is officially stated to be no more than 290,00 ha (Myers)”

Yet early colonial reports from 1910 indicate that the forest area at that time was no more than it is today.

Country Orthodox estimate of forest loss (millions of ha)

Suggested revision

Cote D’Ivoire 13 4.3 – 5.3Liberia 4 – 4.5 1.3

Ghana 7 3.9Benin 0.7 0Togo 0 0Sierra Leone 0.8 - 5 0Total 25.5 – 30.2 9.5 – 10.5

Forests of statistics in West Africa (Fairhead and Leach 1998)

Two thirds of the forest area assumed to have been lost since 1900 is shown by archival and oral historical evidence not to have been forest at that time. Inhabitants have suffered stigma, blame, coercive policies

and loss of resource control for causing a problem that hasn’t happened.

Uganda vegetation history

The semi-deciduous forest zone, Ghana

Rethought as:‘Scar tissue, a recently assembled group of mainly

widespread, well-dispersed species, covering up after some immense disruption of this area and barely infiltrated by rare species which could occur there…. Perhaps widespread farming, elephant damage, or fire and drought (e.g. 1500 AD, 3000 BP, or 8000 BP) has been responsible’

(Hawthorne 1996: 138)

Forests of Statistics in the FAO’s Forest Resource Assessment (Grainger , Journal of Official

Statistics 2007)

‘Every few years we get a new estimate of the annual rate of tropical deforestation. They always seem to show a short time left….in 2000, forest area was down from 1,928m ha to 1,799 m ha,

when the 1990 report gave much the same drop, 1,910m to 1,756 m ha’ (The Guardian, January

2008)

Trends in Natural Forest area 1980–2005 in 90 tropical countries (106 ha) from data in Forest Resources Assessments (FRAs) 1990, 2000, and 2005

Grainger 2008A time series for all tropical forest area, using data from Forest

Resources Assessments (FRAs) of the United Nations Food and Agriculture Organization, is dominated by three successively corrected declining trends. Inconsistencies between these trends raise questions about their reliability, especially because differences seem to result as much from errors as from changes in statistical design and use of new data. A second time series for tropical moist forest area shows no apparent decline. The latter may be masked by the errors involved, but a "forest return" effect may also be operating, in which forest regeneration in some areas offsets deforestation (but not biodiversity loss) elsewhere. A better monitoring program is needed to give a more reliable trend. Scientists who use FRA data should check how the accuracy of their findings depends on errors in the data.