Sustainable mountain development in East Africa in a changing climate

Climate change trends and scenarios and their effect on mountain ecosystems

Observed climate change Mountains are one of the most sensitive ecosystems to climate change in the world (Kohler and Maselli, 2012). Globally, mountainous regions have experienced above average warming during the twentieth century, a trend that is likely to continue in the future (IPCC, 2007). Scientists, therefore, often refer to mountains as early warning systems as they may provide an indication of the changes that lowland ecosystems can expect in the future (Kohler and Maselli, 2012). Specific data on climate change observations and trends in East Africa’s mountainous areas are, however, limited; the available data is mainly for the region as whole. As noted in the IPCC’s Fifth Assessment Report (2013), there is a gap in the research on the long-term climate trends for mountain ecosystems in Africa. According to the IPCC’s Fifth Assessment Report, Africa has seen an increase in temperature by 0.5 °C or more during the last 50 to 100 years. The temperature changes in East Africa are in line with UNDP Climate Change Country Profiles, which indicate that both Tanzania and Kenya have had an increase in temperature of 1.0 °C between 1960 and 2003, while Uganda and Ethiopia have seen an increase of 1.3 °C over the same period (McSweeny et al., 2012 a, b, c, d). Data from weather stations east of the Rwenzori Mountains, located between 960 and 1,869 metres above sea level, indicate an increase in temperature of 0.5 °C per decade since the 1960s (Taylor et al., 2006). Similarly, an increase in

temperature of 0.27 °C per decade has been recorded near Mount Kilimanjaro (Buytaert et al., 2011). In the northern part of the Ethiopian Highlands, the average annual minimum temperature has increased by 0.76 °C between 1954 and 2008, while average annual maximum temperatures have increased by 0.36 °C over the same period. This is significantly higher than the national average of 0.25 °C and 0.10 °C, respectively (Gebrehiwot and van der Veen, 2013). There is less certainty on the observed trends in rainfall across East Africa due to climate models’ difficulties with incorporating the processes affecting the rainfall patterns in the region. Studies presented in the IPCC’s Fifth Assessment Report (2013) show a reduction in rainfall over East Africa during the past 30 years during the ‘long rains’ between March and May/June. Similar findings are reported across the region from Tanzania (Hemp, 2005) and Rwanda (MoNR, 2012) to Ethiopia (William and Funk, 2011). Lower rainfall has also been recorded at Mount Kilimanjaro. Data from three weather stations on the southern slope of Mount Kilimanjaro indicate that precipitation has decreased by up to 39 per cent between 1911 and 2004 (Hemp, 2005). For some areas, the average annual rainfall has remained more or less the same, but records show shifts in the rainy seasons and prolonged dry spells as well as increases in the intensity of rainfall. There is evidence that extreme weather events – both heavy rainfall and droughts – have increased in frequency during the past 30 to 60 years. Based on data from the International Emergency Disaster Database, Shongwe et al. (2010)

noted a significant increase in hydro-meteorological disasters in East Africa, from an average of three events per year in the 1980s to almost 10 per year between 2000 and 2006. The biggest increase was in floods, with an increase from one event per year in the 1980s to seven per year between 2000 and 2006. These disasters affected about 2 million people a year. Future climate scenarios Projections of the future impacts of climate change on East Africa indicate that the current warming trend will continue throughout the twenty-first century. According to the medium-emission scenario of the IPCC’s Fourth Assessment Report, East Africa can expect an average increase in annual temperature of 3.2 °C by 2080; ranging between 1.8 °C and 4.3 °C (IPCC, 2007). The highest increase in temperature is expected in June, July and August. Based on the medium-emission scenario, the temperature will increase by as much as 3.4 °C (ranging between 1.6 and 4.7 °C). Data on climate extremes indicate that the region will experience an increase in warm days and nights as well as an increase in the frequency of heat waves and warm spells (IPCC, 2012; CDKN, 2012). The IPCC (2013) notes that changes in precipitation will greatly affect the climate in Africa. There is a general agreement between the Fourth and Fifth IPCC Assessment Reports (2007; 2013) that East Africa will become wetter, both during the ‘long’ and ‘short’ rainy seasons. Future scenarios predict that the current trend towards a drier climate will reverse. As

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