Yale School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, USA.
Proc Natl Acad Sci U S A. 2012 Oct 2;109(40):16083-8. doi: 10.1073/pnas.1211658109. Epub 2012 Sep 17.
Urban land-cover change threatens biodiversity and affects ecosystem productivity through loss of habitat, biomass, and carbon storage. However, despite projections that world urban populations will increase to nearly 5 billion by 2030, little is known about future locations, magnitudes, and rates of urban expansion. Here we develop spatially explicit probabilistic forecasts of global urban land-cover change and explore the direct impacts on biodiversity hotspots and tropical carbon biomass. If current trends in population density continue and all areas with high probabilities of urban expansion undergo change, then by 2030, urban land cover will increase by 1.2 million km(2), nearly tripling the global urban land area circa 2000. This increase would result in considerable loss of habitats in key biodiversity hotspots, with the highest rates of forecasted urban growth to take place in regions that were relatively undisturbed by urban development in 2000: the Eastern Afromontane, the Guinean Forests of West Africa, and the Western Ghats and Sri Lanka hotspots. Within the pan-tropics, loss in vegetation biomass from areas with high probability of urban expansion is estimated to be 1.38 PgC (0.05 PgC yr(-1)), equal to ∼5% of emissions from tropical deforestation and land-use change. Although urbanization is often considered a local issue, the aggregate global impacts of projected urban expansion will require significant policy changes to affect future growth trajectories to minimize global biodiversity and vegetation carbon losses.
城市土地覆盖变化通过栖息地、生物量和碳储存的丧失威胁生物多样性并影响生态系统生产力。然而，尽管预计到 2030 年世界城市人口将增加到近 50 亿，但对未来城市扩张的地点、规模和速度知之甚少。在这里，我们开发了全球城市土地覆盖变化的空间明确概率预测，并探讨了对生物多样性热点和热带碳生物量的直接影响。如果继续保持目前的人口密度趋势，并且所有具有高城市扩张概率的地区都发生变化，那么到 2030 年，城市土地覆盖面积将增加 120 万平方千米，几乎是 2000 年全球城市土地面积的三倍。这一增长将导致关键生物多样性热点地区的栖息地大量丧失，预计城市增长速度最快的地区是 2000 年城市发展相对较少的东非山地、西非的几内亚森林以及西高止山脉和斯里兰卡热点地区。在泛热带地区，预计高概率城市扩张地区的植被生物量损失将达到 13.8 PgC（0.05PgCy(-1)），相当于热带毁林和土地利用变化排放的约 5%。尽管城市化通常被认为是一个地方问题，但预计城市扩张的全球总体影响将需要重大政策变化，以影响未来的增长轨迹，从而最大限度地减少全球生物多样性和植被碳损失。
