Imhoff Marc L, Bounoua Lahouari, Ricketts Taylor, Loucks Colby, Harriss Robert, Lawrence William T
Biospheric Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
Nature. 2004 Jun 24;429(6994):870-3. doi: 10.1038/nature02619.
The human population and its consumption profoundly affect the Earth's ecosystems. A particularly compelling measure of humanity's cumulative impact is the fraction of the planet's net primary production that we appropriate for our own use. Net primary production--the net amount of solar energy converted to plant organic matter through photosynthesis--can be measured in units of elemental carbon and represents the primary food energy source for the world's ecosystems. Human appropriation of net primary production, apart from leaving less for other species to use, alters the composition of the atmosphere, levels of biodiversity, energy flows within food webs and the provision of important ecosystem services. Here we present a global map showing the amount of net primary production required by humans and compare it to the total amount generated on the landscape. We then derive a spatial balance sheet of net primary production 'supply' and 'demand' for the world. We show that human appropriation of net primary production varies spatially from almost zero to many times the local primary production. These analyses reveal the uneven footprint of human consumption and related environmental impacts, indicate the degree to which human populations depend on net primary production 'imports' and suggest policy options for slowing future growth of human appropriation of net primary production.
人类人口及其消费对地球生态系统有着深远影响。衡量人类累积影响的一个特别有说服力的指标，是我们为自身所用而占用的地球净初级生产量的比例。净初级生产量——通过光合作用转化为植物有机物质的太阳能净量——可以用元素碳的单位来衡量，它代表了全球生态系统的主要食物能量来源。人类对净初级生产量的占用，除了留给其他物种使用的量减少之外，还改变了大气成分、生物多样性水平、食物网内的能量流动以及重要生态系统服务的提供。在此，我们展示一幅全球地图，显示人类所需的净初级生产量，并将其与陆地上产生的总量进行比较。然后，我们得出了世界净初级生产量“供应”和“需求”的空间资产负债表。我们表明，人类对净初级生产量的占用在空间上差异很大，从几乎为零到是当地初级生产量的许多倍。这些分析揭示了人类消费的不均衡足迹及相关环境影响，表明了人类人口依赖净初级生产量“进口”的程度，并提出了减缓未来人类对净初级生产量占用增长的政策选择。
