too hot to handle? Text by Rob Simmons & Phoebe Barnard Photographs by Colin Paterson-Jones The impact of climate change on African

frica is a continent in which the grand sweep of environ- mental change has always beena impressive. Over past millen- nia, rainforests have expanded and shrunk like a pulsing green heart; corridors of open and sunny savan- nas have opened up and then been pinched off. Climate change has always been a fact of life for this con- tinent, one which doubtless helped drive the evolution of inquisitive and problem-solving humans every bit as much as it helped drive the diversi- fication of our extraordinary mam- mals, plants, insects, reptiles and birds. It has been a powerful shaper of the continent’s biodiversity. 

52 climate change these effects than small birds, because they can store resources during good times for use under poorer conditions. But we also know that larger-bodied birds tend to be threatened by other environmental changes, such as habitat fragmentation or pollution. For birds migrating from Europe and Asia, such as storks, eagles, kestrels and rollers, which exploit the vast locust and termite swarms that arise after good rains, we can predict that their long journey south may be increasingly fraught with uncertainty. They may have to spend more time in southern Africa wandering from rainfront to rainfront, thus reduc- ing the time actually spent feeding. The effects of such trends on populations both here and in Europe may be subtle, but could include increased attempts by Palearctic migrants to breed in Africa, later migration departures and arrivals, and overall population declines (see box on page 60). Climate change might not be detri- mental for all species. For some in winter- rainfall areas, for example, higher spring temperatures may be important. Falcon biologist Andrew Jenkins has found a positive link between breeding success and warm spring weather in the south- western Cape. Success is less strongly related to rainfall. If climate changes Blue Swallows are among a suite of species Above The frequency of fire in fynbos is ut that was before 6.45 billion peo- 2001, when the Intergovernmental Panel and eastwards. However, biomes are not mean that seasonal temperatures climb, that may be pushed eastwards from an critical in the life history of the region’s ple (and counting) were crammed on Climate Change (IPCC) produced its likely to move en masse as intact units as universally predicted, Peregrine popu- already tenuous hold in highland areas 8 000-plus plants. Under climate change bonto the planet, more than 850 mil-­ Third Assessment Report, there were few – climate change will affect individual lations could potentially increase, if  towards extinction as temperatures increase. they will probably have to adapt to more lion of them in Africa. The single fact of published field studies in south–central species within them differently, causing frequent burns as temperatures increase human population pressure alters every­ Africa. Since then, a steady trickle has some species relationships to uncouple and soil moisture goes down. thing about the vulnerability of birds, emanated from a number of institutions, (see box on page 60) and ecosystem com- other biodiversity and ecosystems to glo- the precursor to a small flood. Ecologists position to change in complex ways. Previous spread Cape Sugarbirds are bal environmental change, and especially at the South African National Biodiversity Birds in southern Africa are probably intimately tied to the flowering of nectar- climate change. At present there can Institute (SANBI), Kirstenbosch, and the already responding in different ways, rich plants such as this Leucospermum be few starker prospects on the horizon University of Cape Town have modelled some of which may be hard to pre- species. Climatic stresses on the or than the visions of how our world will climate change impacts on the distribu- dict. Unlike birds from temperate climes, on the plant could move either into new change in the next century as a result of tion of plants and biomes, and published such as those in Europe (see box on page territory, breaking the delicate bond us fouling our own nest. For the affluent a popular booklet, The heat is on... impacts 60), many bird species in Africa breed in between pollinator and pollinated. and comfortable among us, it is a mat- of climate change on plant diversity in South response not to rising temperature, but ter of worry, potential discomfort and Africa. These models, which use correla- to rainfall. Rainfall often sparks intense inconvenience, perhaps even danger. For tional techniques to map climate change nesting activity in birds, especially in the poor, though, and especially subsist- effects based on increased temperature, arid regions. Rainfall can also help to ence farmers in Africa, the additional carbon dioxide and reduced soil moisture, predict clutch size and the number of pressure of climate change is potentially predict especially serious impacts on the clutches laid in a season. Most climate devastating. Succulent Karoo biome. Despite the many models foresee reduced and less pre- assumptions underlying this modelling, dictable rainfall over most of southern How will climate change affect it seems that the Succulent Karoo, which Africa. If this proves true, we can expect birds and their habitats in Africa? stretches from ’s Northern that birds will breed less regularly, and Studies of the impact of climate change Cape Province to south-western Namibia, fewer pairs will be successful, under on Africa’s rich diversity have lagged is likely to be fundamentally altered, and lower rainfall regimes. Large birds may badly behind the rest of the world. In other biomes may be shifted southwards be somewhat better ‘buffered’ against james wakelin

54 climate change africa – birds & birding october/november 2005 climate change 55 National Park was predicted to lose a large proportion of the species assessed Climate change effects at a glance that the Succulent Karoo and Fynbos may undergo serious changes, in this study. Because the study was not hat will climate change mean for African birds and ecosys- and could be reduced by 35–55 per cent in the next 50–100 years based on the full distributional limits Wtems? Some fairly stark pointers are provided by thousands of (Fynbos) or, in the case of the Succulent Karoo, virtually disappear. of many of the species modelled, it pages amassed by the Intergovernmental Panel on Climate Change Experimental work by this group has also shown increased mortality may have overestimated the serious- (IPCC). Broadly, temperatures will increase across the globe, faster at of quartz field succulents as a result of increased temperature and albert froneman ness of the effects. For Tawny Eagles, the poles than in the tropics. Antarctica and the Arctic already show ultraviolet light, and enhanced growth of woody species such as Above While larger species such as this they become more successful at rearing German and South African researchers significant temperature-induced ecological changes. Where they are acacias under increased carbon dioxide conditions. Tawny Eagle may be buffered against young. Like so many other ecological noted that even slightly less predictable not constrained by coastlines or other barriers, biomes and species In the context of global change, long-term field studies come the immediate effects of climate change, predictions, this may be complicated by rainfall may contribute to a marked will often shift towards the poles. Rainfall will increase in many tem- into their own. We need lengthy datasets to distinguish the noise their slow breeding rate may make them the effects of climate change on their population decrease. So sensitive is this perate areas and decrease over much of the subtropics. of annual variability from the signal of long-term trends. Using such less able to adapt to the rapid tempo of avian prey, and on the food and life species that its extinction in southern Episodic hazards, such as storms, droughts and fires, are expected data, surveys have documented 15 species of northern hemisphere climatic shifts forecast for future decades. history of that prey. Africa was predicted with only a 10 per to increase in frequency, as are the warm-water El Niño and cold- butterflies moving further north, as expected. The recent extinction Detailed work on what climate change cent drop in mean annual precipitation. water La Niña events which alter regional weather patterns. Many of a cloud forest toad in Costa Rica has been linked to a significant Right The dwarf succulents of the may mean for African vertebrates has Such predictions require field testing, senior scientists are now concluding that sea levels will probably decrease in the frequency of mist, associated with changes in sea Knersvlakte may seem the least likely been much slower than similar work and will hopefully prove incorrect. After rise by up to five metres through displacement – independent of surface temperatures. More than 434 species (trees, shrubs, inver- candidate for susceptibility to increasing done in the northern hemisphere; all, birds, like other species, have been any melting – when the ice sheet in western Antarctica slips into tebrates, fish, mammals, birds) already show recent climate-induced temperatures. However, climate modelling indeed, there are only three published through climate shifts in their evolu- the sea. If the Greenland ice sheet melts, as is expected if global changes in range, 80 per cent in the direction predicted by climatic suggests this biome may completely reports assessing the possible changes tionary history, and have usually been temperatures rise by 3 °C, sea levels might rise by a further seven models. The timing of flowering of trees and egg-laying in birds has disappear by 2080. to African birds and mammals. In their able to adapt somehow to change. The metres. Both seem increasingly likely in the next century. By human also changed significantly in some species. study of birds, mammals, reptiles and worry now is that climate is changing so time frames, these trends are essentially irreversible: it would require When species in an ecosystem respond to change, it is unlikely insects, Barend Erasmus and his col- rapidly, in evolutionary terms, that large a major ice age to re-form ice sheets many kilometres thick. that all react in the same way or at the same speed – as Darwin leagues modelled likely shifts in species birds such as this which breed so slowly realised more than 130 years ago. Thus some species are quite distribution. They showed that 78 per will be unable to adapt in time. How is climate change affecting biodiversity? vulnerable to climate change, but others are not. Species may move cent of species are likely to contract Newer modelling has looked at the wo of the world’s richest biodiversity ‘hotspots’ lie in southern out of the range of others, which could cause the breakdown of their ranges under a climate in which likely prospects for six smaller birds in TAfrica: the Fynbos and Succulent Karoo. In South Africa several mutualisms, such as that between the nectivorous sugarbirds and mean temperature is raised by only 2 °C. South Africa. Together with Richard important modelling exercises have shown what might happen to their food plants. While some are re-sprouters and Most species moved in an easterly direc- Dean, Guy Midgley, Wilfried Thuiller these biomes. The Global Change Research Group of the South can reproduce vegetatively, others are seeders and could face extinc- tion. A few species were expected to and Greg Hughes, we recently used bio- African National Biodiversity Institute at Kirstenbosch has shown tion if the sugarbirds are not around to assist in transferring pollen. become locally extinct, and the Kruger climatic modelling of summer and 

56 climate change africa – birds & birding october/november 2005 climate change 57 Blue Swallow

• occur on mountaintops or slopes; • have restricted ranges or specialised habitat requirements; • occur in the Succulent Karoo, which is likely to be significantly reduced by 2080; • occur at the southern edge of their range in habitats which are likely to be squeezed southwards as tempera- tures increase, for example Fynbos endemics; Mountain • rely on temporary wetlands which may fill less often and remain wet for shorter periods as evaporation rates increase and water resources are pressurised; • are large species with slow reproduc- tive rates; • are island endemics with nowhere to ‘run’.

Based on this, we speculate that among species most at risk in southern Africa will Drakensberg be (from higher to lower risk): Orange- breasted Sunbird, , Vic­ torin’s Warbler, , Knysna Warbler, Yellow-breasted Pipit, Mountain­ Pipit, Hartlaub’s Spurfowl, Violet Wood-Hoopoe, Barlow’s Lark, Herero , Above The stunning visual floral displays winter temperature, rainfall and evapo- Midgley’s team, both nectivores may be Cinnamon-breasted Warbler, Cape Siskin of the Northern Cape may begin earlier if transpiration to assess the probable faced with fewer suitable feeding areas and Protea Canary. Some cliff-nesting vul- spring temperatures are warmer, but could changes to six African birds. and a fragmented functional range. tures occurring at low densities, such as be on a knife edge if spring rains become All are likely to be threatened by climate The largest range decrease in this the Bearded Vulture, may also be at risk if less predictable. change. We looked at pairs of birds rep- study was predicted for the Drakensberg their montane retreats warm significantly resenting species we felt might be at dif- Rockjumper, which was projected to lose and numbers are further reduced below a Potential changes in distributions of South African birds under low- to mid-range Below Of six species of birds assessed for ferent levels of risk. These included two over two thirds of its current range. This minimum critical level. projections of climatic change. The maps on the left illustrate the present distribu- risk to climate change in South Africa, the high-risk species with restricted ranges was expected, as this bird already occurs These are first-cut assessments, and for tion as depicted by Harrison et al (1997), while those on the right indicate the Drakensberg Rockjumper was predicted to confined to high ground or moun- on high slopes and mountaintops and each species we require a better under- probable projections of distribution by the year 2050. All species are projected to lose most of its high-altitude range. taintops (Drakensberg Rockjumper has few places to retreat to as tem- standing of the climatic controls on their lose between 22 and 69 per cent of their present range by 2050. and Blue Swallow), two medium-risk peratures increase. There are also worry- geographic ranges to accurately predict Maps generated by the Global Change Research Group at Kirstenbosch (G. Midgley, species restricted to the Fynbos biome ing predictions for the Blue Swallow, a shifts in range. It is interesting to note, W. Thuiller and G. Hughes). (Cape Sugarbird and Orange-breasted Critically Endangered South African Red though, that only 14 per cent of the 14 Sunbird), and two low-risk species with Data species. Modelling suggests that species (Knysna Warbler and Violet Wood- those species that are typically vagrant wide ranges in South Africa (Mountain by 2050 it will lose about a third of its Hoopoe) are currently listed in the South now should make it all the way past Wheatear and Cape Bulbul). We mod- present range and will move eastwards, African and Namibian Red Data books. northern Namibia, the Kruger National elled the present distribution of each, as out of its high-altitude grasslands and This means that every species should be Park or northern KwaZulu-Natal. They well as its predicted distribution in 2050 into lower areas. It is quite possible that reassessed in terms of climate change may become more common at latitudes based on climate models. this will edge the Blue Swallow close to threat, and a new category – Vulnerability further south in future years, and thereby For each species, our model suggested the brink of extinction in South Africa. to Global Climate Change – could be serve as important indicators of the rate of losses in overall range. The average This approach can give us clues to spe- introduced into future listings. changes to come. range reduction of these six species was cies which are not currently on our Red Several common southern African spe- 40 per cent, and all shifted south- and Data lists, but which may be in need Shifting ranges cies have already shifted their ranges eastwards. The two nectar specialists of urgent conservation attention in the From the twitcher’s point of view, climate in the past few decades, including the declined the least in range, but the near future. There are several initiatives change is good! It will undoubtedly bring Hadeda Ibis, Black Sparrowhawk, Egyptian model took no account of preferred under way that have already begun this vagrant species into our backyards in Goose and, not so recently, the Blacksmith food plants. Given that the producers process of identifying birds across Africa Africa. Take for example Eurasian spe- Lapwing. All these species are resident and of one of their chief nectar sources, that will potentially be influenced by cies that migrate to warm areas with common in South Africa’s Western Cape proteas, show strong declines for some climate change. We predict that these rich food supplies. If temperate parts of Province, but this was not always the case. species in independent modelling by will include species that: southern Africa become more tropical, The lapwing was rarely seen before the 

58 climate change africa – birds & birding october/november 2005 climate change 59 When links in the food chain are broken our examples of European birds becoming ‘uncoupled’ from their young fledged when caterpillar populations were highest, these Fprey by climatic factors have been well studied, and numerous activities have now become uncoupled. other cases may come to light. In a fourth example of uncoupling, the arrival of long-distance Golden Plovers return earlier to their breeding grounds in northern migrating flycatchers in The Netherlands is controlled by day length. Britain, since earlier snow melt exposes potential nesting sites. But The flycatchers, which also rely on caterpillars, arrive on migration the plovers fall short: their insect prey is unavailable when the earliest from Central Africa at the same time as they have done since 1980. chicks hatch, since the insects have not reacted to climate change in However, caterpillars now emerge 13 days earlier than in 1980 – too the same way. Either these plovers will have to move to a new area early for all but the earliest flycatchers. In an attempt to compensate, where they can breed in synchrony with their prey, or they will have to the flycatchers start breeding sooner than they previously did after a time their breeding to prey availability rather than nest site availability. 5 000-kilometre migration. Even so, only the earliest birds succeed in Blue Tits feeding on caterpillars in France and Corsica fell out of matching nestling demands with peak caterpillar biomass. synch with their prey because warmer temperatures advanced the Other examples are coming to light from marine environments, flush of leaves and leaf-feeding caterpillars. Tits normally time their as plankton blooms occur earlier in warmer oceans, often too early breeding to coincide peak nestling demands with peak caterpillar for their fish predators. Potentially, this could generate a significant supplies. As the two became mismatched, with caterpillars peaking breakdown in food chains if it affects fish stocks. Perhaps it is only a too early, adults became energetically stressed, which can reduce temporary mismatch. But while it is an exciting time to study these their lifespan. This may become a familiar theme in food chains, as fast-paced environmental changes, the consequences for birds and shown by another population of tits in The Netherlands. Great Tits ecosystems could be dire. Although African ornithologists have studied there by Marcel Visser did not breed earlier in response to been slow to take up these issues, a joint UCT/SANBI team is looking warming, but their caterpillar prey peaked two weeks earlier than in collaboratively at modelling and testing impacts on African birds’ 1985. Again, although tits used to time their breeding so that their behaviour, breeding, ranges and populations.

early 1940s, and is now common. Hadeda response to climatic events elsewhere. It Ibises were first recorded in the south- seems more probable that climatic factors western Cape in the late 1960s, and are have helped these recent invasions along, now noisily common on lawns and road allowing subtropical species to expand verges. Black Sparrowhawks were rarely into more temperate areas. seen before the mid-1990s, and at present There is no doubt that the contribution 28 breeding and thriving pairs have been of different environmental change factors recorded on the Cape Peninsula. We have will become clearer as more examples seen Little Sparrowhawks with young in are gleaned from this rich continent of pine plantations on the peninsula where ours. Models are only ever as good as the species did not previously occur; their assumptions and predictions, and the closest breeding record was from bioclimatic modelling is evolving rapidly Sutherland in the arid Karoo basin, itself to improve on both those scores. More an outlier, in 1993. important is the need to use the best The traditional reason given for these knowledge and tools we have in order to ‘invasions’ into previously unexploited plan for and adapt to a hotter, drier world areas is the advent of pine and gum plan- in Africa – not to wait for the day when tations for the raptors, and diversified it’s been proven beyond doubt that we are feeding areas, wetlands, and plantations already surrounded by desert.  which allow nesting of some wetland spe- cies. Phil Hockey has argued in this maga- Thanks to Guy Midgley and Wilfried Thuiller zine (Vol.8, No.5) that structural changes (SANBI) for their comments and assistance. in the landscape rather than vegetative tim jackson changes per se appear to be important FURTHER READING The Hadeda may be a recent arrival for birds. So culverts, plantations and Pounds, J., Fogden, M., Campbell, J.H. 1999. pushed into the Western Cape by climatic pylons have made life easier for these ‘Biological responses to climate change on factors rather than the availability of alien overland invaders. However, a closer look a tropical mountain.’ Nature 398:611–615. pine and gum plantations. shows that pine and gum plantations Midgley, G., Rutherford, M., Bond, W. 2001. The have been present in this region since the heat is on... impacts of climate change on plant mid-1800s, yet sparrowhawks, ibises and diversity in South Africa. WWF South Africa. geese only arrived much later. It is hard to Simmons, R.E., Barnard, P., Dean, W.R.J., Midgley, argue that long-distance movers such as G.F., Thuiller, W., Hughes, G. 2005. ‘Climate birds required 150 years to discover these change and birds: perspectives and prospects new habitats as they move rapidly in from southern Africa.’ Ostrich 75:295–308.

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