Secto ral I m pacts
Under the same scenario an estimated 10–48 percent of the Earth’s surface including highly biodiverse regions such as the Himalayas, Mesoamerica, eastern and southern Africa, the Philippines and the region around Indonesia known as Wallacaea would lose their climate space. With limitations on how fast species can disperse, or move, this indicates that many species may find themselves without a suitable climate space and thus face a high risk of extinction. Globally, as in other studies, there is a strong association apparent in these projections between regions where the climate disappears and biodiversity hotspots. Limiting warming to lower levels in this study showed substantially reduced effects, with the magnitude of novel and disappearing climates scaling linearly with global mean warming. More recent work by Beaumont and colleagues using a different approach confirms the scale of this risk (Beaumont et al., 2011, Figure 36). Analysis of the exposure of 185 eco-regions of
exceptional biodiversity (a subset of the so-called Global 200) to extreme monthly temperature and precipitation conditions in the 21st century compared to 1961–1990 conditions shows that within 60 years almost all of the regions that are already exposed to substantial environmental and social pressure, will experience extreme temperature conditions based on the A2 emission scenario (4.1°C global mean temperature rise by 2100) (Beaumont et al., 2011). Tropical and sub-tropical eco-regions in Africa and South America are particularly vulnerable. Vulnerability to such extremes is particularly acute for high latitude and small island biota, which are very limited in their ability to respond to range shifts, and to those biota, such as flooded grassland, mangroves and desert biomes, that would require large geographical displacements to find comparable climates in a warmer world. The overall sense of recent literature confirms the findings of the AR4 summarized at the beginning of the section, with a number
Figure 36: Distribution of monthly temperature projected for 2070 (2.9°C warming) across the terrestrial and freshwater components of WWF’s Global 200. (A) The distribution of 132 terrestrial and 53 freshwater ecosystems, grouped by biomes. (B) Average distance (measured in number of standard deviations from the mean) of 21st century monthly temperatures from that of the baseline period (1961–1990). Terrestrial Ecoregions
Freshwater Ecoregions
a
Tropical/Subtrop Moist Broadleaf Forests (47)
Mediterranean Forests, Woodlands, Scrub (6)
Large Lake (4)
Small Lake (7)
Tropical/Subtrop Dry Broadleaf Forests (8)
Montane Grasslands/Shrublands (9)
Tropical/Subtrop Coniferous Forests (3)
Flooded Grasslands/Savannas (4)
Large River (7) Large River Delta (5)
Small River Basin (21) Xeric Basin (3)
Trop/Subtrop Grasslands, Savannas, Shrublands (8)
Boreal Forests/Taiga (5)
Temperate Grasslands, Savannas, Shrublands (3)
Tundra (5)
Temperate Broadleaf/Mixed Forests (9)
Deserts/ Xeric Shrublands (9)
Temperate Conifer Forests (8)
Mangroves (8)
b
Large River Headwaters (5)
2070 A2 Annual Temperature Distance
Distance
1s
c Source: Beaumont et al., 2011.
2s
3s
4s
Coefficient of variation
53