Please note that this blog no longer accepts comments (there was
too much spam coming in!). If you're reading this blog and want to
respond then please use the contact form on the site.
You can also follow me on twitter.
My latest Mind and Matter column in the Wall
Driving home the other day it occurred to me that almost none of
the greenery I could see-trees, garden shrubs, grass shoulders on
the highway-was going to be used by humans for food, fuel, clothing
That would not have been true 500 years ago. The roadside grass
would have fed horses, the trees would have supplied firewood and
their acorns would have fed pigs. Although the England of my day
has 10 times the population of Tudor times, there's more greenery
for wild nature now than there was then.
Italy has more forest cover than it did 50
years ago, and Austria has doubled its production of greenery over
what it would otherwise be.
Fossil fuels have well known disadvantages, but this is one of
their easily overlooked benefits. By substituting oil and coal for
horses and firewood, we have relieved the pressure on greenery to
supply our needs. By using gas to make fertilizer, we can feed
ourselves from a smaller acreage, leaving more acres for other
A professor in Vienna named Helmut Haberl has been investigating
this phenomenon under the acronym HANPP-or human appropriation of
net primary production (a fancy phrase for greenery or biomass). He
concludes that human beings currently appropriate for themselves
and their domestic animals 14.2% of the world's greenery-including
farms, forests, swamps, grasslands and scrub, but excluding the
oceans. We destroy or prevent another 9.6% of greenery from
growing, by paving or over-grazing; 76.2% remains for nature to
One of Haberl's papers is here. And here is an encyclopedia article summarising
So there is still some headroom for the human enterprise. But I
see an even more encouraging result hidden in Mr. Haberl's numbers.
He finds that the most industrialized parts of the globe do not
necessarily have the largest impact on the biomass of natural
ecosystems, even when you take into account their importation of
primary production from other places.
The reason is that rich economies tend to boost plant growth,
especially on farms, through fertilizer and irrigation. In some
cases they do so to such effect that even a large human
appropriation still leaves lots for other wildlife. Italy, for
example, has more forest cover than it did 50 years ago, yet
produces more food.
Mr. Haberl's native Austria more than doubles its land's
production of greenery over what it would otherwise be.
Consequently, since 1830 Austria has actually reduced the
proportion of biomass it pinches for human use even while
increasing its consumption. Through irrigation, other places, like
the Nile delta, produce more biomass for wildlife than would grow
without human intervention-even after people have appropriated much
of the biomass for themselves.
Here's a homely example. Some of the birds that visit my garden
feed in fields-on seeds, shoots, worms and insects. Man-made
fertilizer boosts the quantity of that food, and therefore of
birds, whose droppings fall in my garden, transferring that
fertility to an ecosystem that will not be harvested, just
View Full Image
John S. Dykes
Almost none of the greenery I could
see-trees, garden shrubs, grass shoulders on the highway-was going
to be used by humans for food, fuel, clothing or shelter.
This means that so long as energy and water are abundant, humans
might eventually aspire to make global appropriation net-negative.
That is to say, our grandchildren could live wealthy consumer
lifestyles consuming huge quantities of plant growth, yet actually
increasing the amount of plant growth available to wildlife above
what it would naturally be.
How would we get there? First, we would stop using the landscape
for biofuels, a catastrophic policy mistake, and help rural
Africans to switch from charcoal to kerosene or solar stoves.
Second, we'd have to find abundant cheap energy with a small land
footprint. That means gas, nuclear and maybe solar. Because
nitrogen fertilizer is made by a reaction between natural gas and
air, abundant gas means abundant fertilizer.