Sustainable mountain development in East Africa in a changing climate

freestanding massif in the world. Highlands are areas that rise above surrounding land with a relatively flat top; the Kenyan and Ethiopian Highlands are examples of such features, the latter being the most well-known in Africa (UNEP, 2014). The mountains support a variety of ecosystems, including Afro-alpine moorlands, forests, scrublands and grasslands. The latter three are the most common type of mountain ecosystems, while Afro-alpine moorland ecosystems are only found at elevations above 3,000 metres. Forests cover a vast area of East Africa’smountains andahighproportionareprotected due to their importance for biodiversity conservation and as water catchment areas. The mountains are home to some of the most diverse tropical montane forests in the world, located in areas such as the Eastern Arc Mountains, the Mau Escarpment, the Albertine Rift, and the Eastern Highlands (Alweny and Gatarabirwa, 2014; UNEP, 2014). These montane forests are also the most important ‘water towers’ in East Africa, providing water for millions of people in highland and lowland communities as well as to important transboundary rivers (UNEP, 2010). Situated near or directly on the equator, East Africa is dominated by a tropical climate, but variations occur between locations and elevations. While vast areas of Kenya and Ethiopia and some areas of Tanzania are semi-arid or arid, most of the mountainous areas have a tropical climate, which are moderated by high elevations and mountain formations (UNEP, 2014). Although it is situated entirely within the equatorial zone, Rwanda, for example, enjoys a cool climate due to its high elevation – nearly all of the country is situated over 1,000 metres above sea level

(REMA, 2011). The combination of cooler and wetter climates in these mountainous areas, coupled with fertile volcanic soil makes the mountain regions very adequate for agriculture. As agriculture is the main source of income for East Africa, the population densities in mountainous areas are generally much higher than in lowland areas (UNEP, 2014). The majority of the region has two distinct rainy seasons: the ‘long rains’ from March to May, and the ‘short rains’, which occur sometime between September and December, depending on the year. The movement of the Inter-Tropical Convergence Zone (ITCZ) over the equator is the main driver of these seasonal rains. Climate variability in the region is mainly caused by changes in the sea-surface temperatures of the tropical eastern Pacific Ocean and

the Indian Ocean. The El Niño–Southern Oscillation (ENSO), caused by changes in the eastern Pacific Ocean, occurs roughly every fifth year resulting in either El Niño or La Niña conditions. During El Niño, ocean temperatures are warmer than normal and lead to wetter conditions in East Africa, while La Niña, which occurs when the ocean becomes cooler than average, brings about drier conditions. Changes in the temperature of the western Indian Ocean, known as the Indian Ocean Dipole (IOD), have similar effects on the region with higher sea-surface temperatures resulting in wetter conditions over eastern and southern Africa (Christensen et al., 2013; Shanahan et al., 2013). The ITCZ is especially sensitive to changes in the temperature of the western Indian Ocean, which affects the onset as well as the duration of rainy periods (McSweeney, New and Lizcano, 2012a).

Simien Mountains National Park, Ethiopia

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