与印度尼西亚这家棕榈油工厂类似的生物燃料计划将增加人类对于地球生物量的使用
(图片提供:AFP/Getty Images)
生物谷:人类给地球留下了一道深深的伤疤,但这里提及的并非人们常说的气候变化。一项新的研究表明,除了过度捕鱼以及对其他资源的榨取外,人类还攫取了全球每年将近1/4的生物量。这一发现意味着,人类活动正在威胁着地球的生物多样性,同时让人不禁对抑制全球变暖的一项主要策略——使用生物燃料以减少二氧化碳排放——提出了质疑。
近几年来,科学家们进行了大量工作,试图确定有多少植被——或者说生物量——被人类占用。然而根据不同的模型以及手头的数据,研究人员最终获得的评估结果却相差很大。为了解决这个问题,由奥地利克拉根福大学的生态学家Helmut Haberl领导的一个研究小组采用了一种新的方法。研究人员分析了来自数据库的大量最新数据,同时考虑了人类活动对全球植物生长造成的影响。Haberl和他的同事对农业产量、森林覆盖状况以及人类活动导致的土壤退化进行了最新的统计学分析,并绘制了相关的图表。
分析表明,仅在2000年,人类便耗尽了当年23.8%的生物生产力。研究人员发现,在人类占用的生物量中,78%与农业有关,剩下的22%则涉及林业、人类引发的火灾以及其他活动。研究小组同时发现,全球各地对于生物量的使用具有显著差异。在这份名单中,南亚人首当其冲,他们占用了该地区63%的植被,这可能是由于当地高密度的农业生产所致。而北美人和中东人占用的植被仅为22%和12%。研究人员警告说,那些大量使用来自农业和林业产品的生物燃料的做法“需要进行慎重考虑”,这是由于这些做法能够使人类使用的生物量翻一番,同时给那些试图分享地球植物的其他物种造成更大的压力。研究人员在本周的美国《国家科学院院刊》(PNAS)网络版上报告了这一研究成果。
美国东兰辛市密歇根州立大学的地球科学家Nathan Moore表示,研究人员的分析是“合理的”,其结果“相当令人担忧”。加利福尼亚州斯坦福卡内基研究所的生态学家Christopher Field对此表示赞同。他说,新的评估结果“基于对最佳可用信息的谨慎判读”。Field警告说:“一个物种占据了全世界陆地近1/4的生物生产力,而数百万物种则只好分享剩余的生物量,很难想象到底有多少物种被挤出了这场竞赛。”Field同样赞成Haberl的研究小组对于生物燃料使用的关注。他说:“对人类而言,并没有足够的生物生产力可以让我们用生物燃料来解决21世纪的能源挑战。”(援引科学网)
英文原文:
News
July 02, 2007
Humans Gobble One Quarter of Food Chain's Foundation
In some areas of the world, up to 63 percent of all the energy produced by plants—energy that would normally fuel native ecosystems—has been pressed into service for humankind
By David Biello
The original farmer probably did not have an outsized impact on the world. Scattering some seeds, guarding them and perhaps clearing a few other species of plants, this proto-agrarian would have been the first to harness the power of photosynthesis for humanitys benefit. Now, thousands of years later, modern agrarians—along with engineers, foresters and consumers—directly control 23.8 percent of all the world's photosynthesis, according to a new analysis.
SELFISH SPECIES?: Humans have appropriated nearly 25 percent of the energy created by photosynthesis in plants, according to a new report.
Using Food and Agriculture Organization statistics through the year 2000 on areas farmed, crops harvested and animals grazed—as well as models of the photosynthetic production of vegetation worldwide and global data on forested areas—ecologist Helmut Haberl of Klagenfurt University in Austria and his colleagues calculated the difference between the energy produced by plants in the absence of humans and the actual amount of photosynthetic energy available to ecosystems after humans have taken their share.
"We found that, due to human activities, in particular past and present land use, 23.8 percent less [photosynthetic energy] remains currently in ecosystems than would be available without human activities," Haberl says.
This affects everything from the diversity of life on Earth to desertification. More than half of the human share of photosynthetic energy comes from farming, but other forms of land use contribute 40 percent and human-caused forest fires a full 7 percent.
And the burden is not evenly spread. The human share, for example, is as high as 63 percent in southern Asia and as low as 11 percent in central Asia and Russia. Technologies such as industrial fertilizers have helped to lower the human burden by increasing harvests while limiting land area, but this increasing agricultural output has been confined to certain regions of the globe, Haberl notes.
HUMAN IMPACT: Humanity's share of worldwide photosynthetic production is not evenly distributed as shown in this map. Click on the image for a larger version.
As the human population continues to rise in coming years, Haberl and his colleagues expect the human share to eat up more and more of the available biomass."On a global scale, our preliminary—so far unpublished—results strongly indicate, in any case, that [the human share] is on the rise and has been so [for] the past 300 years," Haberl says.
And that share could rise explosively should a shift to biofuels occur on a broad scale. Such a shift might result in a doubling of crops harvested in coming decades, Haberl adds, "something that could have massive impacts on ecosystems, above all their resilience and biodiversity" as energy is shifted from feeding animals to fueling cars. Already Haberl has shown in other papers how land-use changes on a local scale undercut the complex web of life in Austria—from breeding bird species to crickets to the plants themselves—and endangered its ability to thrive.
That relationship will be explored in the much larger North and South American context next, Haberl says. Nevertheless, it is already clear that "a remarkable share of global [photosynthetic production] is used to satisfy the needs and wants of just one species on earth," as the researchers write in Proceedings of the National Academy of Sciences USA
原始出处:
PNAS, Proceedings of the National Academy of Sciences of the United States of America
"Quantifying and mapping the human appropriation of net primary production in the Earth's terrestrial ecosystems"
Helmut Haberl, K. Heinz Erb, Fridolin Krausmann, Veronika Gaube, Alberte Bondeau, Christoph Plutzar, Simone Gingrich, Wolfgang Lucht, Marina Fischer-Kowalski
http://www.pnas.org/
原始出处:
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