Prof Steve Jones has a unique solution to solving the world's global
NEXT week's great extravaganza of science, the meeting of the British
Association for the Advancement of Science at Cardiff, has (among
sessions on "The Day the Sun Goes Out", "Computers in Engineering" and
"Exploding Custard") a whole morning devoted to "Forestry: A Growing
Challenge". The message is simple - England, the barest country in
Europe, needs more trees.
The real issue, though, is not too few of those leafy objects, but too
many. Scientists are warning of a new ecological problem: a rapid
spread of forests that is threatening the world's landscapes.
Some mistake, there, surely? We all know that the rainforest is being
destroyed, and that the fires around Athens this summer were the worst
there have ever been. In many places, though, timber is not in retreat,
but in swift advance. In my favourite bolt-hole in southern France the
markets sell photographs of the villages taken from old postcards. They
are bought mainly by locals, who look wistfully at streets without S-
reg Volvos or mime-artists, but the biggest change is not in the people
but in the scenery.
Fifty years ago, the rocky hills of Languedoc were almost bare because
they were grazed by sheep or terraced into tiny vineyards. Now, the
land has been abandoned; and, in some places, the amount of cover has
gone up by 15 times. The trees are taking over, and there are thousands
of acres of oak and pine on what was once farmland. The same is true
all over southern Europe, and the great Mediterranean Forest is today
bigger than it has been for centuries.
Ecologists are alarmed: birds such as the Dartford Warbler, the Serin,
the Stonechat and the Linnet - all inhabitants of open scrub - are in
rapid retreat and are being replaced by common woodland birds found
throughout Europe. The Black Wheatear, a lover of rocky places, was
declared extinct in France two years ago. The scrublands of the
Mediterranean contain 20,000 species of flowering plant, most of which
die as soon as they are shaded out. Some nature-lovers are calling for
the fires to be allowed to burn to rescue the flowers and the birds
from their gloomy fate.
Trees are galloping across the United States, too. A recent meeting of
the Ecological Society of America heard that, with global warming,
there are more summer rains in the deserts of the south-west, and that
this "Arizona monsoon" is predicted to increase over the next century.
A simple experiment on watering the shrubby oaks that dot the hillsides
shows that, when it does, they will produce three times as many
seedlings as before.
The greenhouse effect comes, of course, from carbon dioxide in the
atmosphere, up by a third since the Industrial Revolution. That gas,
too, stimulates tree growth; and a test on Texas trees shows that the
increase above natural levels likely within the next century will
double the number of plants that survive. If that is not enough, the
other great air pollutant, nitrogen, does its bit. There is plenty of
it in car exhausts, and it falls miles away from the cities, spurring
the growth of distant forests.
The Volvo as the friend of the tree means that a third of America's
open deserts and scrub may soon be covered by forest. That causes
concern; not just because the Lone Ranger will have to carry a machete,
but because the country's precious national parks are threatened. No
doubt, the sound of the conservationist's chain-saw will soon be heard
in the land.
However, the woody plague hit the United States long before air
pollution. In the Shenandoah Valley, in Virginia, growth rings in the
largest trunks show that, at the time of the Indians, fires were set
every five years or so. Many of the early travellers commented on the
park-like landscape, with open grasslands and not much standing timber.
Today's Shenandoah National Park, though, is in the main an
impenetrable, and strictly protected, woodland.
Trees are inexorable things, always ready to take over as soon as they
get the chance. At the end of the last ice age, seeds preserved in peat
show that spruce and pine followed the glaciers northwards at a mile a
year - which means that Birnam Wood could easily have marched on
Dunsinane (some 10 miles away) within Macbeth's lifetime.
Something must be done to stop the forests before it is too late. The
message that the British Association should pass on to the ecology
movement is clear: Save the Planet! Chop Down a Tree!
from the climate change list: <email@example.com>
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