Environment - July 28
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Humans appropriate 24% of Earth's productivity
Human landscapes occupy 35% of the planet's ice-free land surface
Researchers have developed the first geographically detailed analysis of humankind's impact on the biosphere, as represented by a metric known as HANPP or human appropriation of net primary production. The results are presented and discussed in two papers published in the July 6 online edition of the journal Proceedings of the National Academy of Sciences.
Using vegetation modeling, agricultural and forestry statistics, and geographical information systems data on land use, land cover, and soil degradation that localizes human impact on ecosystems, a team lead by Helmut Haber of Austria's Klagenfurt University show that humans are presently appropriating 23.8% of potential net primary productivity -- 15.6 pentagram of carbon per year. Of this amount, 53 percent of appropriation results from harvest, 40% from land-use-induced productivity changes, and 7% from human-induced fires. The work shows that humans are having a massive impact on Earth's resources.
"Our research has documented that Humans are indeed becoming a force in changing the global environment," David Zaks, a research assistant at the University of Wisconsin - Madison's Center for Sustainability & the Global Environment (SAGE), told mongabay.com. "The importance of these studies lies in reframing previously benign numbers into a story that more effectively portrays our collective actions on the planet."
The researchers present a series of maps that show how humans are appropriating the planet's resources. Zaks says that in most areas background productivity has decreased due to human activities, though in some areas it has been artificially increased through intensive fertilization, irrigation and mechanization of agriculture
(25 July 2007)
Below are excerpts from the two papers mentioned. -BA
Quantifying and mapping the human appropriation of net primary production in earth's terrestrial ecosystems
Various authors, Proceedings of the National Academy of Sciences (PNAS)
ABSTRACT: Human appropriation of net primary production (HANPP), the aggregate impact of land use on biomass available each year in ecosystems, is a prominent measure of the human domination of the biosphere.
We present a comprehensive assessment of global HANPP based on vegetation modeling, agricultural and forestry statistics, and geographical information systems data on land use, land cover, and soil degradation that localizes human impact on ecosystems. We found an aggregate global HANPP value of 15.6 Pg C/yr or 23.8% of potential net primary productivity, of which 53% was contributed by harvest, 40% by land-use-induced productivity changes, and 7% by human-induced fires.
This is a remarkable impact on the biosphere caused by just one species. We present maps quantifying human-induced changes in trophic energy flows in ecosystems that illustrate spatial patterns in the human domination of ecosystems, thus emphasizing land use as a pervasive factor of global importance. Land use transforms earth's terrestrial surface, resulting in changes in biogeochemical cycles and in the ability of ecosystems to deliver services critical to human well being.
The results suggest that large-scale schemes to substitute biomass for fossil fuels should be viewed cautiously because massive additional pressures on ecosystems might result from increased biomass harvest.
(6 July 2007)
The full paper is available online.
Our share of the planetary pie
Jonathan A. Foleyâ€ , Chad Monfreda, Navin Ramankutty, and David Zaks
The rise of modern agriculture and forestry has been one of the most transformative events in human history. Whether by clearing natural ecosystems or by intensifying practices on existing croplands, pastures, and forests, human land-use activities are consuming an ever-larger share of the planet's biological productivity and dramatically altering the Earth's ecosystems in the process. Although the character of land use varies greatly across the world, ranging from industrialized croplands, grazing on marginal lands, managed timber lots, animal feedlots, or biofuel plantations, the ultimate outcome is the same: the production of forest or agricultural goods for human needs taken at the expense of natural ecosystems.
...Will the future growth of human land use come at the expense of continued ecological degradation (7) or rely on the unsustainable crutches of fossil fuels and fossil water?
Ultimately, we need to question how much of the biosphere's productivity we can appropriate before planetary systems begin to break down. 30%? 40%? 50%? More?
Or have we already crossed that threshold?
(23 July 2007)
Unfortunately, this commentary is behind a paywall.
China cancels environmental report
Mitchell Landsberg, Los Angeles Times
An assessment of 'green GDP' would have calculated the cost of pollution to its rapidly growing economy.
BEIJING â€” From a public relations standpoint, it didn't look good. In the space of less than a month, China had quashed two potentially embarrassing environmental reports that would have said what most people already know: This is a country facing a costly and increasingly deadly environmental crisis.
First, in early July, reports surfaced that China had successfully lobbied the World Bank to redact portions of an environmental assessment that calculated how many people were likely to die prematurely as a result of air pollution.
Then, late last week, the government announced that it was canceling plans to publish a "green GDP" report that would have calculated the cost of pollution to China's rapidly growing economy, as measured by its gross domestic product.
The decisions, on their face, appeared to suggest reluctance at the top of China's government to acknowledge the seriousness of environmental degradation that has caused the worst air pollution in the world, and water pollution that has left millions of people without local sources of potable water.
Chinese and Western experts, however, said Monday that authorities might have acted for reasons not readily apparent to casual observers. They said the reluctance to publicize the country's environmental woes might have had more to do with political relations between the central government and provincial leaders than with a fear of airing dirty laundry.
(24 July 2007)