Man, do we have big feet

harvester.jpgGuessing how many species there are — or were before the human steamroller got cranked up — on this unique planet has become something of a parlor game for biodiversity scientists. The truth is that we don’t have a very good idea, which is not surprising give that so many of our fellow life forms are bacteria, soil mites, roundworms, parasites, and otherwise obscure microscopic bugs.  Some experts guesstimate that there are a few million, others say maybe 20 or 30 million. 

But there is something that we do know now, with considerably more precision: of those — let’s say three million — species, a single one now sucks up roughly a quarter of all of earth’s biological production.  Can you guess which species that is?  Well, duh.  

One in every four sunbeams that falls on an upturned plant and miraculously transforms dirt into life, or that could have done so, ultimately ends up in our hamburgers or paper-mill forests or cornfields destined for biodiesel, or has been blocked from the miraculous transformation by the asphalt under our cars or the baking roofs of our buildings on which our AC units are merrily buzzing.  

Remember the backpacking T-shirts from the old days (maybe they still make them) emblazoned: “Take only memories, leave only footprints”? That’s one helluva footprint.  

A new, comprehensive analysis concludes that humans now appropriate 23.8% of the planet’s total net primary productivity, of which 53% was contributed by harvest, 40% by land-use-induced productivity changes (for example, paving paradise to put up a parking lot), and 7% by human-induced fires. 

haberl_et_al_pnas_hanpp.jpg

That is a global average.  Looking closer, we should not be surprised to find that the figures are much higher for heavily populated areas.  Map b shows the “Human Appropriation of Net Primary Production” (HANPP) as a fraction of the potential net primary productivity — in other words, the fraction used by humans of the plant biomass that could be produced in an area, given local environmental conditions. Notice that the global average of one quarter is actually a gross underestimate for heavily populated areas. Throughout north central North America, much of Europe, all of the Indian subcontinent, China, and southern Australia, the situation is code red, so to speak — we are using between 60 and 100% of potential primary production.  One might say that, in those places, we are very close to the edge. And that doesn’t leave much left over for the other 2,999,999 (or so) species.

So how will we solve the central problem of our time, making the transition away from fossil fuel to alternatives, while feeding a doubling population?  Through massive land clearance for cultivation of biofuel crops?

Not.

The original citation is:

Haberl, H.,  K.H. Erb, F. Krausmann, V. Gaube, A. Bondeau, C. Plutzar, S. Gingrich, W. Lucht, and M. Fischer-Kowalski. 2007. Quantifying and mapping the human appropriation of net primary production in earth’s terrestrial ecosystems. Proceedings of the National Academy of Sciences 31:12942-12947 (6 July 2007).

About Emmett Duffy

I am a Natural Patriot and an ecologist with expertise in biodiversity and its importance to human society. My day job is Professor of Marine Science at the College of William and Mary in Virginia.
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3 Responses to Man, do we have big feet

  1. Pingback: on-linehg » Blog Archive » Man, do we have big feet

  2. shaw says:

    It is a little bit alarming when you think about what we are doing to the planet. We may be following in the same path as other dominant species that get to big, and then cause their own extinction. But I wonder, we may be a species that is also aware and conscious about what we are actually doing to the environment. So, when you think about it, we may be able to turn things around. In small ways we think we are, but the question is, can we do it fast enough, or are we doomed to failure.

    In the end, we really will have to come together as a global community to save the planet… Shaw

  3. It’s so sad , we are the dominant and the most intelligent specie in the planet yet we are the most destructive , countless animal and plant species have gone extinct because of us , the ecosystem is now under tremendous strain thanks to our insatiable appetites.

    If only we’ll use our intellect to help the planet instead of causing it’s deterioration the world will be a much better place to live in.