Predator is the prey

14/08/2000
Down To Earth

Predator is the prey smog is not only suffocating human beings, but is also choking plants. Air pollution is indirectly responsible for the destruction of trees and, for the first time, researchers of Finland have found evidence supporting their argument. According to them, due to air pollution there has been a decline in the population of predator species, which eat insects that destroy the plants. This has happened either because pollution makes these predators less active or it kills them. Hence, when the predator population decreases, the insect population increases, leading to a destruction of plants.

Elena Zvereva and Mikhail Kozlov of the University of Turku in Finland studied the affect of a beetle Melasoma lapponica, on willow trees in the forests near a nickel-copper smelter on the Kola Peninsula, in northwest Russia. This is one of the world's most polluted spots.

The researchers measured pollution levels at 10 sites, up to 36 kilometres from the smelter each year between 1993 and 1998. They also checked the density of adult beetles at the sites and collected data regarding the number of predator attacks. The findings of the research show that though predators killed more Mlapponica at polluted sites than at relatively clean ones, the number of these predators at polluted sites was very less.

This meant that, overall around twenty per cent more insects survived in polluted sites. Head counts of the wood ant, a predator of the beetle, confirmed that its numbers had declined in areas where smog was worst.

Zvereva says their work highlights the importance of long-term studies to find out the effects of pollution on plants ( Journal of Applied Ecology , Vol 37, p298).

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