By Donella Meadows
–July 18, 1991–
In 1986 a group of ecologists at Stanford published a paper in the journal Bioscience that made scientists’ hair stand on end. They calculated that human beings now control 40 percent of the planet’s land-based net primary productivity.
That number would have hit the front pages, if more people had understood what it meant.
The “net primary productivity” (NPP) is the amount of the sun’s energy caught by green plants and fixed into biomass (minus the amount the plants use for their own metabolism). It’s the net growth of all plants in a year, and therefore it’s the base of all food chains. Every other creature on earth eats plants — or eats something that eats plants — or eats something that eats something that eats plants.
Which is to say, the NPP is the energy stream that powers all life. According to the Stanford ecologists direct human consumption — what we eat, what we feed our animals, the fish we catch, the wood we harvest — adds up to only three percent of global NPP.
Where we have our real impact is in our indirect co-option of NPP — the flow of energy we channel into communities of organisms other than the ones in natural ecosystems. That flow includes the total production of croplands and grazing lands, the forest we kill by trashing and burning, and the loss of NPP as cities and manmade deserts spread.
Direct and indirect human uses of nature add up to 25 percent of the NPP of the entire planet and 40 percent of the NPP on land. That’s a conservative estimate. It doesn’t count losses to toxic wastes, acid rain, ozone depletion, greenhouse gases and other forms of pollution, which are hard to measure. It could be that 100 percent of nature is ALTERED by humanity, but 40 percent (on land) is what we CONTROL.
The Stanford authors say, “an equivalent concentration of resources into one species and its satellites has probably not occurred since land plants first diversified.” And we still have expansion plans. The human population is expected to double in 35-40 years. To improve living standards the economy will have to double faster than that. If it does, within 20-30 years virtually all the primary productivity of the planet will fall under human control.
What would the world be like then?
Some ecologists say it would be like England or Holland, where nearly every inch of land is managed for human purposes. Others point out that those countries import grain, wood, paper from outside their borders. They live above their NPP budget, because other countries live below theirs — something the world as a whole cannot do. Better examples of an economy at the 100 percent NPP limit, some say, might be the Sahel or Bangladesh or the most crowded parts of India or China.
One thing is certain: as more of the earth’s NPP is diverted to human purposes, less is available to the millions of species we do not farm or harvest. The wave of extinctions is already underway. The survivors will be what one ecologist calls our “fellow travelers and running dogs” — housecats and coyotes, chickens and pigeons, wheat and thistles, cattle, fleas, viruses.
One of the ecologists who made the NPP calculation, Paul Ehrlich, has described the consequences: “few warblers and ducks and more starlings and herring gulls, fewer native wildflowers and more noxious weeds, fewer swallowtail butterflies and more cockroaches, smaller herds of elk and bigger herds of rats, less edible seafood, less productive croplands, less dependable supplies of pure freshwater, more desert wastes and dust storms, more frequent floods, and more uncomfortable weather.”
Wilderness would be gone. For us the world would probably be liveable, but with diminished options. We would live on the biological edge. The planetary cycles that maintain us would be less resilient. At some point, as we eliminate species, the whole interwoven fabric of nature could unravel. We don’t know where that point is. Says Peter Vitousek, another of the Stanford ecologists, “The world’s going to hell while we research this interesting question.”
At the 100 percent NPP limit, any further expansion on our part would have to come from more efficiency rather than more encroachment. We would have to feed grain directly to people instead of animals, to burn wood in more efficient stoves, to recycle biological materials more tightly. We would finally have to control our numbers and our waste.
The choice is whether we achieve that self-control 20-30 years from now, or now — while there are still songbirds, still wildflowers, still forests that are not plantations and wetlands that are not landfills, rice paddies, or fish farms. The choice is whether we want every last bit of the NPP, or whether we want to leave some for the bears and the moose, the whales and the dolphins, the loons that call across the northern waters, the geese that make Vs across the sky.
By continuing to expand, we are in fact silently, unknowingly, choosing. We’re deciding that we want it all for ourselves. And we’re gambling that we can control it all without making fatal mistakes.
Copyright Sustainability Institute 1991