Living with Global Warming

Policy Reports | Global Warming

No. 278
Wednesday, September 14, 2005
by Indur M. Goklany

Global Population at Risk with and without Climate Change

Table I - Magnitude of Problem

Table I, based on the results of the DEFRA-sponsored studies noted above, indicates the total population at risk from malaria, hunger, water shortage and coastal flooding in 2085 assuming: (a) no climate change, and (b) unmitigated emissions. In addition to providing the global population at risk from hunger, this — and subsequent — tables also show estimates of the corresponding changes in global cereal production, a surrogate for global food production.

"Studies sympathetic to mitigation show that adaptation is preferable."

Table II provides estimates of the reduction in total global population at risk under each of the four mitigation scenarios — from the least stringent mitigation scenario — the Kyoto Protocol — on the left, to the most stringent, “no climate change” scenario, on the right.

Let us look at the hazards individually. In particular, I will compare the relative costs and benefits of amelioration through what I will call “focused adaptation” against those due to different mitigation scenarios.

"Global warming will have a minor effect on malaria."

Malaria. Table I shows that the current population at risk from malaria will grow from 4.4 billion today to 8.8 billion in 2085, even in the absence of climate change, due to increased population in developing countries where the disease is epidemic. This is about 80 percent of the projected world population in 2085, according to the scenario used in the DEFRA-sponsored studies. Climate change would add only marginally to the population at risk in 2085, due to an increase in the range of mosquitoes, for example, to higher altitudes. Table II shows that:

  • The Kyoto Protocol would reduce the total number of people at risk in 2085 by 0.2 percent while costing, as noted previously, about $165 billion in 2010 alone.
  • Reductions in the population at risk of malaria from stabilization at either 550 ppm or 750 ppm would be even smaller, amounting to 0.4 percent and 1.3 percent, respectively, while costing trillions of dollars.15
  • Curiously enough, stabilizing CO2 at 750 ppm would reduce the total global population at risk for malaria in 2085 more than stabilization at 550 ppm — by 1.3 percent versus 0.4 percent. The reason: climate change will alter temperature and precipitation patterns in ways that sometimes will favor mosquito propagation and malaria transmission, and at other times will not.
  • Halting further climate change as of 1990 (if that were possible) would at best reduce the total problem of malaria in 2085 by 3.2 percent.
Table II - Percent Reduction in Total Population at Risk in 2085

But, according to the World Health Organization (WHO),16 malaria’s current annual death toll of one million could be halved with annual expenditures of $1.5 billion or less (in 2003 dollars)17 by attacking present-day vulnerabilities, through such measures as further development and better delivery of public health services for — and research targeted at — better treatment and prevention of malaria.

"Malaria's one million annual death toll could be cut in half for $1.5 billion annually."

Therefore, even if the WHO’s cost estimate is overly optimistic by an order of magnitude, the benefits of reducing current populations’ vulnerability to malaria now would be much greater and cost significantly less than actions proposed under the Kyoto Protocol.

Notably, developing and/or instituting adaptive measures — technologies, practices and institutions — to reduce vulnerability to malaria today will also help reduce malaria tomorrow, whether the risk of disease is due to warming or unrelated factors. These measures would reduce risks to 100 percent of the global population at risk today and in 2085, while mitigation would at most address the problem of only 3.2 percent of the at-risk population in 2085, and an even smaller proportion of the billions of people at risk annually between now and then.

Perhaps even more important, reducing malaria in developing countries today would enhance those countries’ adaptive capacity. It would improve public health, and assure fuller development of their human capital and potential for economic development, which would enhance their resiliency and reduce their vulnerability to any adversity, whether caused by warming or another agent.18

Hunger and Food Production. Today, at least 521 million people worldwide are at risk of hunger. The good news is that their numbers are expected to fall to 300 million in 2085, despite an increase in global population, due to continuing increases in agricultural productivity. However, global warming is expected to partly offset that decline, exposing an additional 69 million to 91 million people to food shortages by 2085. This would occur due to a slight fall in the rate of global agricultural productivity growth, as changing weather patterns increase drought and reduce soil moisture in many developing areas. As with malaria, stabilizing CO2 concentrations at 750 ppm would reduce the total global population at risk for hunger in 2085 by a greater amount than pursuing stabilization at 550 ppm. The reason is that fertilization from atmospheric carbon benefits crops, and the CO2 concentration under the 750 ppm stabilization pathway is higher than under the 550 ppm pathway.

Table II also indicates that post-1990 warming would be responsible for 21 percent of the total global population at risk for hunger by 2085. This amount, seemingly large, is, in fact, the result of a small (1.9 percent) warming-related drop in future global food production between 1990 and 2085. In effect, unmitigated warming would reduce the annual growth in food productivity from 0.84 percent per year to 0.82 percent per year.19 But in the 1990s the world spent about $33 billion annually on agricultural research and development (R&D), including $12 billion in developing countries. Therefore increasing R&D investment, say, by $5 billion per year, should more than compensate for the 0.02 percent annual shortfall caused by unmitigated warming, particularly if the additional investment is focused on solving current agricultural problems in developing countries that might otherwise be exacerbated by warming.20 Thus, as shown in Table II:

  • Meeting the Kyoto Protocol’s emission reduction targets would reduce the population at risk of hunger by approximately 1.5 to 2 percent in 2085.
  • Stabilizing CO2 emissions at 550 ppm would reduce the population at risk of hunger by approximately 9.7 percent in 2085.
  • By contrast, investing an additional $5 billion to solve agricultural problems that developing countries face today would reduce the population at risk of hunger by 50 percent — beginning today, and in 2085, and in the intervening years.

"Investing $5 billion a year in agricultural research could cut world hunger in half, whereas spending 30 times as much on emissions reductions would, at best, reduce hunger less than 2 percent."

The agricultural problems of developing countries include growing crops in poor climatic or soil conditions. Should warming cause such conditions to spread, agriculture might have to expand further into areas with low soil moisture or too much water, or soils that are highly saline, alkaline or acidic. Thus actions to improve current agricultural production under marginal conditions would alleviate hunger in the future whether or not the climate changes. Similarly, since science cannot predict increases in CO2 and temperatures in any particular area, crops should be developed to take advantage of such conditions as and when they develop. But even if we don’t know what changes will occur precisely where, we can make substantial progress on these approaches in the short-to-medium term.21 Such focused measures should be complemented by measures that would broadly increase agricultural productivity.22

By 2085, the measures outlined above would not only help reduce the 80 million increase in global population at risk for hunger due to unmitigated warming, but also the 300 million at risk due to factors unrelated to warming.23 Equally important, they would do more than any mitigation efforts to reduce global population at risk for hunger in the interim, whether it is 521 million people in 1990 or 300 million in 2085 (Table I). Moreover, the additional R&D investment is relatively modest compared to the costs associated with the Kyoto Protocol.

This approach would also boost the adaptive capacity of developing countries by improving public health, enhancing human capital and economic growth, and in turn reducing their vulnerability to any adversity, whether caused by warming or another agent.24 Furthermore, this approach would produce other benefits, including:

  • Reduced demand for additional agricultural land by increasing food production per unit of cultivated land. This would limit conversion of habitat to agriculture, which is the biggest threat to global terrestrial biodiversity. Reducing habitat fragmentation and loss of migratory corridors would, in turn, help species adapt more “naturally” via migration and dispersion, and also conserve carbon stores and sinks (for sequestration of carbon removed from the atmosphere) and, thereby, aid mitigation.25
  • As discussed below, reduced demand for agricultural water will help overcome what could be the major future constraint on meeting global food needs — insufficient water26 — and reduce pressure on global freshwater biodiversity.

"Reducing agricultural water use 18 percent would double the availability of water for all other uses."

Water Shortages. Today, 1.75 billion people face shortages of fresh water suitable for irrigation or industrial and household uses. This is expected to increase to 6.5 billion people by 2085, due to the increasing population of poorer countries. Global warming may increase the number at risk by nearly 13 percent (862 million) in 2085 — or it may have a positive effect, cutting the population at risk by more than a third (37 percent), or 2.4 billion people. Mitigation will produce, at best, marginal benefits, but may do more harm than good:

  • Meeting the Kyoto Protocol’s emission reduction targets would, at best, reduce the population facing water shortages by 1 percent in 2085 — and could, in fact, exacerbate the problem.
  • Stabilizing CO2 emissions at 550 ppm would, at best, reduce the population facing water shortages in 2085 by 860 million, but could increase the population at risk by 2.4 billion.

Table II indicates that warming might, in fact, reduce water shortages in some areas. The actual affect depends on changes in weather patterns that occur with global warming, which climate models are currently unable to project accurately on a regional basis. Thus mitigation would make matters worse for people in these areas — reducing, if not eliminating, net water-related benefits from mitigation. This unfortunate outcome also holds for other hazards for which warming results in a mix of positive and negative outcomes, such as food production. By contrast, adaptation allows communities to capture the benefits of warming while reducing, if not avoiding, the downsides. And measures taken to reduce water shortages now will also help relieve them in the future.

Measures that would help societies cope with present and future water shortages regardless of cause include institutional reforms to treat water as an economic commodity by allowing market pricing and transferable property rights to water. Such institutional reforms should stimulate widespread adoption of existing but underused conservation technologies, and lead to more private sector R&D investment that would reduce the demand for water by all sectors — for example, by developing new or improved crops and techniques to increase agricultural water use efficiency. Private sector spending should be supplemented by additional public sector resources.

Improvements in water conservation following such reforms are likely to be most pronounced for the agricultural sector, which is responsible for 85 percent of global water consumption.27 An 18 percent reduction in agricultural water consumption would, on average, double the amount of water available for all other uses, including household, industry and in-stream uses (such as recreation and conservation of aquatic species). The last would reduce pressures on freshwater biodiversity due to water diversion, which, as noted, is the greatest threat to freshwater biodiversity.

"Coastal barriers and planned retreat would address flooding at a cost of $1 billion a year."

Coastal Flooding. Today, 10 million people are at risk of coastal flooding, and this number is projected to increase by 3 million by 2085 as coastal populations increase. If there is any hazard for which emission reductions ought to be more cost-effective than adaptation, it is coastal flooding. By 2085, the studies underlying Table II project that unmitigated warming will raise the global sea level by 0.41 meters (16 inches)28 — due to such factors as melting ice sheets, storm surges and thermal expansion — putting an additional 81 million people at risk and thus contributing 86 percent of the total global population at risk of coastal flooding. However, the risk of flooding to coastal population can be reduced, if not eliminated, for relatively little additional investment:

  • Meeting the Kyoto Protocol’s emission reduction targets would reduce the total population at risk from coastal flooding in 2085 by 18 percent
  • Stabilizing CO2 emissions at 550 ppm would reduce the total population at risk from coastal flooding by approximately 80 percent in 2085.29
  • By contrast, investing an additional $1 billion annually in preventive measures — like building sea walls and other hardened structures and an orderly relocation of coastal populations — would address this problem just as well, if not more effectively.30

Thus significant emission reductions would not only cost more but could also provide less protection in 2085 than an adaptive approach that would protect against flooding.

Table III - Projected Changes in Extent of Various Ecosystems%2C with and without Climate Change

"Development and agriculture could cause a greater reduction in global forests and wetlands than global warming for the foreseeable future."

Pressures on Natural Systems: Global Forests and Coastal Wetlands. Table III compares projected changes in the global area of forests and coastal wetlands with and without unmitigated climate change. Due to development and agriculture, the forested area of the world is expected to fall 25 percent to 30 percent by 2050 and the area of coastal wetlands are expected to decline 40 percent by 2085. The major risk to biodiversity is the loss of natural habitat to development. Increased levels of atmospheric CO2 favor plant growth; however, the effects of global warming on sea levels and weather patterns could reduce wetland areas. Between now and 2085, global warming could increase forested areas by 5 percent; but it could reduce the area of coastal wetlands another 13 percent. Whether increases in global forest area can be sustained beyond that under the unmitigated emissions scenario is another matter.

Table III also indicates that unless baseline problems are addressed relatively quickly, a substantial portion of currently existing global forests and wetlands might be converted to other uses, and the benefits of mitigation may arrive too late to stem the loss of habitat (and biodiversity).

As previously noted, many steps taken now to reduce hunger and water shortage — such as enhancing food productivity per unit of land and water — would in fact decelerate, if not forestall, further diversion of land and water to human uses and reduce habitat fragmentation. This is illustrated for land conversion by Figure I, which indicates the inverse relationship between cropland demand and increases in average annual agricultural productivity. It shows that if agricultural productivity increases by 1.0 percent per year between 1990 and 2085, rather than the 0.84 percent estimated under the unmitigated emissions scenario, the area devoted to cropland could be reduced by 13.7 percent without worsening global hunger, all else being equal.31

Enhancing agricultural productivity would, therefore, reduce the socioeconomic cost of setting aside any land or water for in situ conservation,32 which is one of the goals of the 1992 UN Convention on Biological Diversity. It would also reduce the costs associated with carbon sequestration. Moreover, reducing habitat loss and fragmentation would advance one of the principal objectives of the UN Framework Convention on Climate Change enshrined in Article 2, namely, to allow ecosystems to adapt naturally to climate change.

It is often argued that adaptation is inferior to mitigation because the former does not adequately reduce the impacts of climate change on natural systems.33 But, as the foregoing discussion indicates, adaptation can, indeed, relieve pressures on natural systems. Over the next few decades adaptive steps taken now could more effectively conserve biodiversity than any mitigation efforts.34

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