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Table 5

Population at Risk in 2085 for Malaria (millions)

Baseline 1990

2085

Population at risk in the absence of climate change

4,410

8,820

Additional population at risk because of climate change

256 to 323

Total population at risk

4,410

9,076 to 9,143

Source: N. W. Arnell et al., "The Consequences of CO2 Stabilization for the Impacts of Climate Change," Climate

Change 53 (2002): 413­46.

carbon from the atmosphere (i.e., "sink" car-

controlling diseases in general and malaria in

bon in the biosphere), the expanse of cropland

particular. In other words, today's wealthier

(a crude measure of the amount of habitat

and more technologically advanced societies

converted to agricultural uses, which is per-

have greater adaptive capacity, and that is

haps the single largest threat to global terres-

manifested in the current geographic distribu-

Malaria is

tion of malaria prevalence around the globe.50

trial biodiversity),52 and the expanse of coastal

functionally

wetlands.

The fact that malaria is a significant health

Table 6, derived from the FTA, summa-

risk only in the poorest of countries reaffirms

eliminated in a

rizes the impact that warming might have on

the importance of incorporating adaptive

society whose

these ecological indicators in each of the four

capacity--and changes in future adaptive

annual per capita

scenarios discussed thus far.

capacity due to economic growth and techno-

Under each scenario, net carbon sink capac-

logical change--into impact assessments. In

income reaches

ity is higher in 2100 relative to 1990 because

fact, analysis suggests that malaria is function-

$3,100.

the positive effect of carbon fertilization will

ally eliminated in a society whose annual per

capita income reaches $3,100.51 But as shown

not have been offset by the negative effects of

higher temperatures during that period. Sink

in Table 1, even under the poorest (A2) sce-

capacities under the warmest scenarios (A1FI

nario, the average GDP per capita for develop-

and A2) are approximately the same in 2100,

ing countries is projected to be $11,000.

and greater than the sink strengths under the

Hence, few, if any, countries ought to be below

cooler scenarios (B1 and B2).

the $3,100 threshold in 2085. Moreover, given

Partly for the same reason and also

the rapid expansion in our knowledge of dis-

because of its low population, the amount of

eases and development of the institutions

cropland is lowest for the A1FI world, fol-

devoted to health and medical research, the

lowed by the B1 and B2 worlds. (Cropland

$3,100 threshold will almost certainly drop in

estimates were not provided for the A2 sce-

the next several decades as public health mea-

nario). Thus, through the foreseeable future,

sures and technologies continue to improve

the A1FI scenario would have the least habi-

and become more cost-effective.

tat loss and, therefore, pose the smallest risk

to terrestrial biodiversity, while the cooler

Ecological Changes in

scenarios would have the highest habitat

2085­2100

losses.

Regarding the loss of coastal wetlands, esti-

mated losses due to sea level rise for each sce-

Thus far, we've examined the impact of cli-

nario are substantial. But the contribution of

mate change on human well-being. But cli-

climate change to total losses in 2085 is small-

mate change will also affect global ecology. In

er than losses due to subsidence from other

particular, climate change will have an impact

manmade causes.53 Table 6 shows that total

on the terrestrial biosphere's ability to remove

11