10 CONVENIENT SOLUTIONS TO AN INCONVENIENT TRUTH
marine and other natural ecosystems provide a range of services often not recognized in national economic accounts but vital to human welfare: regulation of water flows and water quality, flood control, pollination, decontamination, carbon sequestration, soil conservation, and nutrient and hydrological cycling. Sound ecosystem management provides countless benefits to, and opportunities for, human societies, while also supporting the web of life. Ecosystem services and biodiversity conservation contribute to environmental sustainability, a critical Millennium Development Goal and a central pillar of World Bank assistance. Research undertaken as part of the Millennium Ecosystem Assessment showed that, over the past 50 years, human activities have changed ecosystems more rapidly and extensively than at any comparable period in our history. These changes have contributed to the achievement of many net development gains, but at growing environmental and social costs: habitat loss, land degradation, and reduced access to adequate water and natural resources for many of the world’s poorest people. Climate change is likely to compound this environmental degradation. Terrestrial and oceanic ecosystems play a significant role in the global carbon cycle (see figure 1.1). About 100 gigatons of carbon (GtC) annually are taken up and released by terrestrial ecosystems, and another 100 GtC are taken up and released by marine systems (Matthews and others 2000). These natural fluxes are large compared to the approximately 6.5 GtC emitted annually from fossil fuels and industrial processes and another 1–2 GtC per year emitted as a result of deforestation, predominantly in the tropics (Gitay and others 2002). Natural habitats are a net sink of carbon. Worldwide, soils alone store almost 2,000 GtC (Matthews FIGURE 1.1
Approximate Stores (Gigatons) and Fluxes (Gigatons per Year) of Carbon >100a 100
atmosphere 750+ 100
>100
plants soil 2,000
6.5
oceans 800
coal oil gas 10,000
40,000
Source: Woods Hole Institute (http://www.whrc.org/carbon/index.htm). Note: Numbers in the boxes are carbon stores. Numbers beside the arrows are carbon fluxes. a. Deforestation contributes 1–2 GtC per year.