Climate change and Africa: an ecological perspective
Volume 4 Number 2 - July 2007
Jon C. Lovett
Climate change and ecology
By burning fossilised plants for energy huge quantities of carbon dioxide have been pumped into the Earth’s atmosphere. Unlike smoke or smog it cannot be seen, but so much has been burnt that the concentration of atmospheric carbon dioxide has measurably increased. There are a number of interesting ecological changes that appear to be related to this increase. Firstly, as any botanist knows, the normal concentration of carbon dioxide is a limiting factor for photosynthesis. Plants, or at least some plants, can grow faster when there is more CO2, a prediction confirmed by research on native African plants at the South African National Biodiversity Institute (SANBI, 2007). This increased growth has knock-on ecological effects. For example, comparison of old photographs with modern landscapes by Professor William Bond of the University of Cape Town, shows that in South Africa at least, woody plants are invading grasslands (pers.comm., 2006). These changes in vegetation then cause changes in the hydrology of water catchments. Now it is necessary to stop and think for a moment. Usually when human impact on vegetation is considered it is in relation to a particular development, perhaps ploughing a field or felling a forest. However, increased CO2 is different because of the vast scale of the change, which is everywhere. In the South African example the concern is that the entire grassed catchment area of the Drakensberg range will be affected causing substantial changes to South Africa’s water supply.
The second ecological effect of increased CO2 is caused by its role as a ‘green-house gas’. Together with some other gases, such as methane, CO2 acts as a planetary blanket that slows down the release of the Sun’s warmth from the Earth’s surface. The situation is complicated by factors such as cloud cover, but the general scientific consensus now is that an observed increase in global temperatures results from the increase in greenhouse gases, notably CO2. Again the vast scale of changes needed to be considered. Climate determines the extent of the major vegetation formations and in a warmer world whole biomes are on the move. Not all the plants can keep up; research by Wendy Foden on the Quiver Tree (Aloe dichotoma) in Namibia shows that populations in the northern part of the range are dying as the area experiences more drought conditions (Foden, 2002; in press). More southerly trees are doing well with young plants regenerating. However the change is happening so fast that it is hard for a long-lived and slow growing species such as the Quiver Tree to keep up. Vegetation models of the Cape Floristic kingdom by SANBI scientist Guy Midgley show that this extra-ordinary area of plant diversity will be much reduced under future climate scenarios with a huge number of extinctions predicted (Hannah et al., 2005, Lovett, 2005a, 2005b).
Although much of the recent research on plants and climate change has been carried out in South Africa, with some dramatic conclusions, the impacts will be continent-wide (McClean et al., 2006; McClean et al., 2005). When global temperatures increase there are huge changes to the world’s weather systems with all sorts of knock-on effects. For example, Africa produces about half of the world’s dust, much of it coming from the Sahara and Sahel. The dust modifies climate by reflecting solar energy, provides nutrients for carbon-dioxide absorbing plankton in the ocean and helps fertilize Amazon soils. If rainfall in the Sahara and Sahel were to increase thereby causing increased vegetation cover, and there are indications that this is currently the case, then there could be changes in Sahel are also associated with a higher frequency of Atlantic hurricanes. Extreme weather conditions that can cause great economic damage in countries around the Gulf of Mexico seem to start in the highlands of Ethiopia, travel westwards across Africa and then over the Atlantic to wreak havoc on the sea-board of the USA and Caribbean countries. However, long-term predictions are for a drier western Africa and expansion of the Sahara southwards into what are now the Congo rainforests (see Figure 1). Interestingly, it appears that this has happened before during previous global climate change as the present-day forests are growing on desert sands. Models of vegetation shifts suggest that forest plants will move southwards into Angola and up into the mountains of the central rift. The wetter parts of central Africa, which are the coastal regions of Cameroon and Gabon, are predicted to retain more plant diversity than elsewhere, as are the mountains of eastern coastal Africa. Compared with the past, these predictions match locations of proposed African rainforest refugia, even though the refugia were during times of a colder, drier climate instead of a hotter one. There are several possible reasons for this. Firstly it is rainfall that determines where the rainforests are. So in times of drought the rainforests will contract in both hotter and drier climes. Secondly, mountains tend to be wetter as they act as condensers of moisture; and thirdly, mountains offer plants the chance to move to a different climate in a short distance. Simply by going up a few hundred metres in elevation a plant can find a cooler habitat, unlike the poor Quiver Tree, which has to move hundreds of kilometres.
Climate change and society
Humans live under all kinds of climatic conditions. In Africa people live on high altitude grasslands, in the deep forest and driest deserts. But the type of climate plays an important role in how societies are organised and if the climate changes then social structures will need to change too. This can be seen in African history. Drying of the
Sahara from about 5300 years ago has been associated with the rise of the Pharaohs along the Nile. Collapse of the city of Mapungubwe in 1290 AD in southern Africa and subsequent rise of Great Zimbabwe can be linked to drought followed by a wetter climate. More recently, drought contributed to the ecological shocks of cattle disease and small pox experienced in eastern Africa at the end of the 19th century, known by the Maasai as the Emutai period. The rains failed completely in 1897 and 1898. The Austrian explorer Dr Oscar Baumann, who travelled in Maasailand in 1891, wrote chilling eyewitness accounts of the horror experienced by the Maasai people:
“There were women wasted to skeletons from whose eyes the madness of starvation glared ... warriors scarcely able to crawl on all fours, and apathetic, languishing elders. Swarms of vultures followed them from high, awaiting their certain victims.”
(Baumann 1894, Masailand) History looks set to repeat itself. The world was faced with similar scenes from Eritrea during the 1980s and recently the UN Secretary General Ban Ki-moon suggested that the Dafur crises was due to drought and conflict between settled farmers and nomadic herders over scarce water supplies – problems which he linked to climate change. The Intergovernmental Panel on Climate Change states that Africa is the continent most vulnerable to climate change with an increase in both the frequency and severity of droughts and floods. The 1991-1993 drought in south-eastern Africa affected about 100 million people, where-as floods in the region in 2000 reduced Mozambique’s annual economic growth rate from 8% to 2%. At the same time as World leaders have agreed on Millennium Development Goals to reduce poverty and improve environmental sustainability, climate change is unzipping the fabric of societies caught up in its effects.
Scientific investigations of climate change have been warning for some time that human activities that increased atmospheric concentrations of greenhouse gases could have global effects, leading to a concerted international policy response. The United Nations Framework Convention on Climate Change entered into force on 21 March 1994; most countries have signed up to it, and it has been ratified by 191 countries. At the first conference of the parties in Berlin in 1995 it was decided that there needed to be a stronger protocol containing detailed commitments for industrialized countries. This lead to the Kyoto Protocol being adopted at the third conference of the parties in Kyoto on 11 December 1997, which listed the industrialized countries that needed to take action in an annex, leading them to be called the ‘Annex 1 countries’. However, the individual needs of nations made it difficult for State governments to ratify the Protocol as there was considerable concern about the economic impacts of limiting greenhouse gas emissions in economies largely dependent on burning fossil fuels for power and transport. Moreover there was also concern about the principle of ‘differentiated but common responsibilities’ in which developing countries (called the non-Annex 1 countries) did not have any commitments under the protocol. To many this might seem fair, after all, why should developing African nations have to curtail their economic growth to counter a problem that was not of their making? But not all developing countries have the carbon footprints of those in Africa. Of particular concern in 1997 was the potential economic rise of India and China, both non-Annex 1 counties in the Kyoto Protocol and so not subject to any controls on greenhouse gas emissions. This led the United States senate to pass the Byrd- Hagel Resolution in July 1997 by 95 votes to 0:
Resolved, That it is the sense of the Senate that—
(1) the United States should not be a signatory to any protocol to, or other agreement regarding, the United Nations Framework Convention on Climate Change of 1992, at negotiations in Kyoto in December 1997, or thereafter, which would—
(A) mandate new commitments to limit or reduce greenhouse gas emissions for the Annex I Parties, unless the protocol or other agreement also mandates new specific scheduled commitments to limit or reduce greenhouse gas emissions for Developing Country Parties within the same compliance period, or
(B) would result in serious harm to the economy of the United States; and
(2) any such protocol or other agreement which would require the advice and consent of the Senate to ratification should be accompanied by a detailed explanation of any legislation or regulatory actions that may be required to implement the protocol or other agreement and should also be accompanied by an analysis of the detailed financial costs and other impacts on the economy of the United States which would be incurred by the implementation of the protocol or other agreement.
Eventually the Kyoto Protocol entered into force on 16 February 2005, primarily because of ratification by the European Community and Russia. But by this time the fears expressed in the Byrd-Hagel resolution had come to pass as some non-Annex 1 countries have become major economic players and carbon emissions from China look set to exceed those of the United States in a few years time.
Mitigation and adaptation
Even in the face of the scale and magnitude of climate change there are things that can be done. The Kyoto Protocol contains a series of measures aimed at reducing greenhouse gas emissions, known as mitigation, most notably the Clean Development Mechanism (CDM). The CDM allows Annex 1 countries to offset their emissions by investing in emission reduction projects in developing countries. This flexible approach is regarded as a ‘win- in’ strategy by policy-makers as developing countries benefit whilst developed countries are able to meet their Kyoto commitments. South Africa was the first African country to launch a CDM project with approval of the Kuyasa low-cost urban housing energy upgrade project in Cape Town. This focuses on renewable energy and energy efficiency by fitting solar water heaters, insulated ceilings and low energy light bulbs in existing low cost houses. Another form of mitigation that has attracted a lot of interest from conservationists is the potential for obtaining CDM payments to cover the cost of forest conservation on the grounds that carbon lost through deforestation will contribute to greenhouse gas emissions. From a conservation perspective this is a ‘winwin’ in that forest biodiversity will be protected whilst preventing CO2 emissions, however this avoided deforestation policy is a long way from gaining acceptance. In addition to energy reduction projects, as in the Kuyasa example, carbon could be sequestered in plantations, or biofuels could be planted to replaced oil-based transport fuels in developed countries. However, Africa as a continent has not yet taken full advantage of the funds available under the CDM and there is more that could be done. A controversial suggestion for mitigating South Africa’s own emissions, and an approach that is much discussed in developed countries, is an expansion of nuclear power to replace energy derived from coal-fired power stations. South Africa has operated a nuclear power plant at Koeberg near Cape Town since 1984 and has substantial stocks of uranium. But the nuclear option comes with its own ecological problems notably the possibilities of an accident and disposal of waste.
It is also getting a little late for completely effective mitigation as global warming is already upon us. Political impasse on international agreements for greenhouse gas reductions means that CO2 levels will continue to rise. The world is left with adaptation. For Africa, adaptation means coping with extreme droughts, floods and a rising sea level. It is necessary to bear in mind the social impacts of global warming when discussing ecological adaptation and what botanists have to do to cope with the present changes. From a policy perspective an important step is to integrate the ecology of global climate change into the Convention on Biological Diversity. For example the Global Strategy for Plant Conservation, which contains important agreements such as protection of 50% of the world’s important plant areas (IPAs) by 2010, needs to include provisions for the movement and extinction of plants in a warmer world. It will be selfdefeating if a lot of effort is put into protecting areas that are home to plants that will either no longer grow in the IPA or are dead. So for in situ conservation it is necessary to focus on the places that will be buffered from climate change, protect places where plants will move to and create corridors to help plants move into safety. Those plants at risk of extinction because their habitat will change and unable to move fast enough to find a new home, need to be helped to move and bring them into cultivation or seed-banks ready for a return to the wild when possible. All of this will require a major co-ordinated effort for which botanic gardens are well placed. Not only for direct conservation action, but also education about the effect of global warming and the potential mitigation measures that everyone can participate in – from energy reduction to tree planting.
Jon C. Lovett
- Foden, W.B., 2002. Mortality of Aloe dichotoma (the Quiver tree) in the Succulent Karoo, South Africa – are the effects of climate change already apparent? MSc Thesis, University of Cape Town.
- Foden, W., Midgley, G.F., Hughes, G., Bond, W.J., Thuiller, W., Hoffmann, M.T., Kaleme, P., Underhill, L.G., Rebelo, A. and Hannah, L. (in press). A changing climate is eroding the geographical range of the Namib Desert tree Aloe through population declines and dispersal lags. Diversity and Distributions.
- Hannah, L., Midgley, G., Hughes, G. Bomhard, B., 2005. The view from the Cape: extinction risk, protected areas, and climate change, BioScience 55(3): 231-242. http://scholar.google.com/ accessed 25th June, 2007.
- Lovett, J.C., 2006. Climate and society, African Journal of Ecology 44: 421-422. http://www.blackwell-synergy.com/toc/aje/44/4 accessed 25th June, 2007
- Lovett, J.C., Midgley, G.F., & Barnard, P. 2005a. Climate change and ecology in Africa, African Journal of Ecology 43: 167-169. http://www.blackwell-synergy.com/toc/aje/43/3 accessed 25th June, 2007
- Lovett, J.C., Barnard, P., & Midgley, G.F., 2005b. National Climate Change Conference in South Africa, African Journal of Ecology 43: 279-281. http://www.blackwell-synergy.com/toc/aje/43/4 accessed 25th June, 2007
- McClean, C.J., Doswald, N., Küper, et al., 2006. Potential impacts of climate change on Sub-Saharan African plant priority area selection, Diversity and Distributions 12: 645-655.
- McClean, C.J., Lovett, J.C., Küper, W., et al., 2005. African Plant Diversity and Climate Change, Annals of the Missouri Botanical Garden 92: 139-152.
- SANBI, 2007. South African National Biodiversity Institute http://www.sanbi.org/research/climatechange.htm
- Sommer, H., Küper, W., Lovett, J. & Barthlott, W., 2005. The future of Africa’s plant diversity – potential effects of climate change on species distributions. Poster at the South African National Climate Change Conference, 17-21 October 2005 in Midrand, South Africa.
- Sommer, H., Küper, W. &. Barthlott, W., 2006. Implications of climate change on Africa’s plant diversity. Talk at the ESSP Open Science Conference: Global Environmental Change - Regional Challenges, 9-12 November in Beijing, China.
Centre for Ecology, Law and Policy
University of York
York YO10 5DD UK
and Technology and Sustainable Development Group
University of Twente, Enschede, The Netherlands