Abstract
Climate change impacts the structure, functioning, and distribution of species and ecosystems. It will shift ecosystem boundaries, potentially affecting vulnerable ecosystems, such as tropical Africa's high mountain ecosystems, i.e., afroalpine ecosystems, and their highly susceptible uniquely adapted species. However, ecosystems along these mountains are not expected to respond similarly to the change. The ericaceous woody vegetation, located between the low-elevation broadleaf forests and high-elevation afroalpine vegetation, are anticipated to be affected differently. We hypothesize that projected climate change will result in an upward expansion and increasing dominance of ericaceous vegetation, which will negatively impact the endemic rich afroalpine ecosystems of the extensive Sanetti plateau. Hence, we modeled the impact of future climate change on the distribution of ericaceous vegetation and discussed its effect on bordering ecosystems in the Bale Mountains. We applied four familiar correlative modeling approaches: bioclim, domain, generalized linear methods, and support vector machines. We used WorldClim’s bioclimatic variables as environmental predictors and two representative concentration pathways (RCPs) of the IPCC Fifth Assessment Report climate change scenarios, namely RCP4.5 and RCP8.5 for future climate projection. The results indicate increased ericaceous vegetation cover on the midaltitude of northwestern and northern parts of the massif, and the Sanetti plateau. We observed upward range expansion and increase of close ericaceous vegetation in midaltitudes, while receding from the lower range across the massif. Moreover, the current ericaceous vegetation range correlates to the temperature and precipitation trends, reaffirming the critical role of temperature and precipitation in determining species distributions along elevational gradients. The results indicate the high likelihood of considerable changes in this biodiversity hotspot in Eastern Africa.
Highlights
The recent climate change induced warming is the most pervasive of the various threats to the planet’s biodiversity[1,2,3]
Three out of the four of the IPCC Fifth Assessment Report (AR5) Representative Concentration Pathways (RCPs) predicted moderate to severe climate warming throughout the coming century in response to changes in radiative forcing arising from anthropogenic emissions of greenhouse gases and a erosols[6]
Tropical African high mountain ecosystems, i.e., afroalpine ecosystems, occur in isolated patches restricted to peaks of the high volcanic mountains along the Great Rift Valley and Cameroon-Nigeria Mountain ranges between Tropic of Capricorn and Tropic of Cancer[19,20]
Summary
The recent climate change induced warming is the most pervasive of the various threats to the planet’s biodiversity[1,2,3]. Climate change will likely induce thermal isotherm shifts increasing the risk of disrupting the stability of afroalpine mountain ecosystems and affecting the unique plant diversity. This can lead to unexpected taxonomic and functional reorganization of communities and massive extinctions of endemic s pecies[1,3,7]. Mountains are complex landforms that uniquely contribute to biodiversity They are important in investigating climate change impact on individual species and ecosystems. The ericaceous vegetation is a vital component at the transition between broadleaf forests and afroalpine vegetation It has a broad distribution range, high thermal tolerance, dispersal ability (wind dispersal), and adaptation potential. Soft Erica shoots are often grazed and browsed by domestic stock, and the fire-killed Erica stumps are collected for firewood by locals
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