Desertification and a shift of forest species inthe West African Sahel

Climate Research

Patrick Gonzalez¹ 

关键词: Desertification;    Forest biodiversity;    Land cover change;    Natural regeneration of forest species;    Senegal;    Vegetation zone shift;    West African Sahel;   

DOI  :  10.3354/cr017217

来源: Inter-Research Science Publishing

【 摘 要 】

ABSTRACT: Original field data show that forest species richness and tree density in the West African Sahel declined in the last half of the 20th century. Average forest species richness of areas of 4 km² in Northwest Senegal fell from 64 ± 2species ca 1945 to 43 ± 2 species in 1993, a decrease significant at p < 0.001. Densities of trees of height ≥3 m declined from 10 ± 0.3 trees ha^-1 in 1954 to7.8 ± 0.3 trees ha^-1 in 1989, also significant at p < 0.001.Standing wood biomass fell 2.1 t ha^-1 in the period 1956-1993, releasing CO₂ at a rate of 60 kgC person^-1 yr^-1. These changes have shifted vegetation zones toward areas of higher rainfall at an average rate of500 to 600 m yr^-1. Arid Sahel species have expanded in the north, tracking a concomitant retraction of mesic Sudan and Guinean species to the south. Multivariate analyses identify latitude and longitude, proxies for rainfall and temperature, asthe most significant factors explaining tree and shrub distribution. The changes also decreased human carrying capacity to below actual population densities. The rural population of 45 people km^-2 exceeded the 1993 carrying capacity, forfirewood from shrubs, of 13 people km^-2 (range 1 to 21 people km^-2). As an adaptation strategy, ecological and socioeconomic factors favor the natural regeneration of local species over the massive plantation of exotic species.Natural regeneration is a traditional practice in which farmers select small field trees that they wish to raise to maturity, protect them, and prune them to promote rapid growth of the apical meristem. The results of this research provide evidence fordesertification in the West African Sahel. These documented impacts of desertification foreshadow possible future effects of climate change.

【 授权许可】

Unknown