Air pollution poses threat to crop yields

[Guest guest]

http://www.guardian.co.uk/uk_news/story/0,3604,616645,00.html

Air pollution poses threat to crop yields

Brown, environment correspondent

Tuesday December 11, 2001

The Guardian

Two new air pollution threats to Britain which could wipe out vulnerable

plant species, cut crops yields of wheat and potato by 20% and affect human

health, have been identified by scientists working on a government study.

Traffic fumes and industrial pollution from as far away as the US, China and

India threaten to push ozone levels in the lower atmosphere over the danger

limit. Southern England is particularly vulnerable because ozone is already

close to the danger threshold because of home grown pollution from cars and

factories.

So concerned is Meacher, the environment minister, about the

findings, released yesterday, that he is to raise the matter with fellow EU

ministers at a meeting in Brussels tomorrow. He said that a new

international agreement to cut ozone pollution, on the same lines at the

climate change convention was required to tackle the threat.

Low level ozone, caused by the action of sunlight on car and factory

emissions, has long been a problem in Europe. There has been a successful

programme of reducing emissions which caused dangerous peaks of pollution in

the summer, but while these problems have been tackled the general

background levels of ozone have continued to rise.

This means that within a few years the levels of ozone could be permanently

above the levels where they begin to hurt people's lungs and cause crop

damage.

Staple crops like wheat, potatoes, peas and beans are all vulnerable to 20%

declines in yield at relatively low levels of ozone.

Fowler, chairman of the national expert group of transboundary air

pollution, said: " There is a cocktail of pollutants which travel long

distances. We have a common pool of air across Europe, and now we have

increasing background levels of pollutants round the entire northern

hemisphere. We need international cooperation to stop them passing dangerous

thresholds. "

The second problem is caused principally by industrial farming methods in

Britain. Ammonia from slurry, which rapidly breaks down into nitrogen, is

blown in the wind and deposited in wild places on upland areas of Britain

fertilising the soil.

In parts of the south west, Wales and Cumbria, nitrogen deposits are 20

kilogrammes per hectare, 10 times above the natural background.

The problem is that the species that have adapted to live in these poor

soils, like heather, are overtaken by other species like grass which thrive

on fertiliser. Particularly vulnerable are specialist plants like sundew

which supplement its diet by eating insects.

In a nitrogen rich world, it would not need to do this but would be swamped

by taller invading plants. Already there is evidence that endangered plants

that live in poorer soils in nature reserves are being wiped out by

invaders.

The Department of Environment is producing a consultation paper in the

spring to try and find ways of controlling ammonia emissions from farming.

But not all the news was bad yesterday. Acid rain caused partly by sulphur

dioxide emissions from power stations has been cut by 50%. The acid prevents

fish breeding and kills many of the small creatures in the water.

For the first time, some of the lakes and rivers in Wales, the Pennines,

south west Scotland and parts of the Highlands are showing signs of

recovery, a process that could take 100 years.