The 21st Century climate challenge

2Climate shocks: risk and vulnerability in an unequal worldLosses of biodiversity aremounting in many regions.Climate change is one of theforces driving these trends.Over time it will becomea more powerful forceway. Losses of ecosystems and biodiversityare intrinsically bad for human development.The environment matters in its own right forcurrent and for future generations. However,vital ecosystems that provide wide rangingservices will also be lost. The poor, who dependmost heavily on these services, will bear thebrunt of the cost.As in other areas, the processes of climatechange will interact with wider pressureson ecosystems and biodiversity. Many of theworld’s great ecosystems are already underthreat. Losses of biodiversity are mounting inmany regions. Climate change is one of theforces driving these trends. Over time it willbecome a more powerful force.The rapidly deteriorating state of the globalenvironment provides the context for assessingthe impact of future climate change. In 2005,the Millennium Ecosystem Assessment foundthat 60 percent of all ecosystem services wereeither degraded or being used unsustainably. 93The loss of mangrove swamps, coral reef systems,forests and wetlands was highlighted as a majorconcern, with agriculture, population growthand industrial development acting togetherto degrade the environmental resource base.Nearly one in four mammal species is in seriousdecline. 94Losses of environmental resources willcompromise human resilience in the face ofclimate change. Wetlands are an example.The world’s wetlands provide an astonishingrange of ecological services. They harbourbiodiversity, provide agricultural, timberand medicinal products, and sustain fishstocks. More than that, they buffer coastaland riverside areas from storms and floods,protecting human settlements from sea surges.During the 20 th Century, the world lost halfits wetlands through drainage, conversion toagriculture and pollution. Today, the destructioncontinues apace at a time when climatechange threatens to generate more intensivestorms and sea surges. 95 In Bangladesh, thesteady erosion of the mangrove areas in theSundabarns and other regions has underminedlivelihoods while increasing exposure to risingsea levels.Climate change is transforming the relationshipbetween people and nature. Many ecosystemsand most species are highly susceptible to shiftsin climate. Animals and plants are adapted tospecific climate zones. Only one species has theability to adjust the climate through thermostatsattached to heating or cooling devices—and thatis the species responsible for global warming.Plants and animals have to adapt by moving.Ecological maps are being redrawn. Overthe past three decades, the lines markingregions in which average temperaturesprevail—‘isotherms’—have been movingtowards the North and South Poles at a rateof about 56 kilometres per decade. 96 Speciesare attempting to follow their climate zones.Changes in flowering seasons, migratorypatterns and the distribution of flora andfauna have been detected across the world.Alpine plants are being pushed towards higheraltitudes, for example. But when the pace ofclimate change is too rapid, or when naturalbarriers such as oceans block migration routes,extinction looms. The species most at risk arethose in polar climates, because they havenowhere to go. Climate change is literallypushing them off the planet.Climate change has already contributedto a loss of species—and global warming inthe pipeline will add to that loss. But fargreater impacts will take off at 2°C overpreindustrial levels. This is the threshold atwhich predicted extinction rates start to rise.According to the IPCC, 20–30 percent ofplant and animal species are likely to be atincreased risk of extinction if global averagetemperature increases exceed 1.5–2.5°C,including polar bears and fish species thatfeed on coral reefs. Some 277 medium orlarge mammals in Africa would be at risk inthe event of 3°C warming. 97The Arctic under threatThe Arctic region provides an antidote to theview that climate change is an uncertain futurethreat. Here, fragile ecological systems havecome into contact with rapid and extremetemperature increases. Over the past 50 years,mean annual surface temperature in areas from102 HUMAN DEVELOPMENT REPORT 2007/2008