Deep-rooted benefits

Organic farming boosts biodiversity of all species

Published on:

15 Nov 2004, 12:00 am

organic farming increases biodiversity at every level of the food chain -- all the way from the humble bacteria to mammals. This is the conclusion of the most comprehensive review of worldwide studies that compared organic farming with conventional agricultural practices. Previous studies had shown that organic farming merely benefits wildlife around the farms.

The review was conducted by two groups of researchers -- one from English Nature, a uk government agency supporting wildlife conservation, and the other from the Royal Society for the Protection of Birds -- who had no vested interest in organic farming. Data from Europe, Canada, New Zealand and the us was analysed. Typically, each of the 76 studies reviewed measured biodiversity in groups of organisms ranging from bacteria to earthworms, beetles, mammals, birds and plants. Of the 99 separate comparisons of groups of organisms, 66 found that organic farming benefited wildlife, eight concluded it was detrimental and 25 produced mixed results or suggested there were no differences between both the farming methods (see table: Diverse delight).

Diverse delight Organic farms benefit every level of the food chain
Taxon	Positive affect	Negative affect	Mixed/no difference made
Birds	7*		Z
Mammals	2
Butterflies	1		1
Spiders	7		3
Earthworms	7	2	4
Beetles	13	5	3
Other arthropods	7	1	2
Plants	13		2
Soil microbes	9		8
Total	66**	8	25

According to the researchers, organic farming aids biodiversity by using fewer pesticides; by adopting wildlife-friendly management of habitats where there are no crops; including strategies such as not weeding close to hedges; and through mixed farming: a combination of arable and livestock farming. Such methods particularly benefit some bird species. Lapwings, for example, nest on spring-sown crops, but raise their chicks on pasture; intensive agriculture has lead to an 80 per cent decline in their population in England and Wales.

In North America, higher species richness and overall abundance (on an average, 2 and 2.6 times greater respectively) were seen on organic farms than conventional farming fields. Another reviewed study from the uk points to benefits for bats -- two species, the greater and lesser horseshoe bats, were found only on organic farms. For all the species, foraging activity was 84 per cent more on organic farms, suggesting that bats preferred such habitats.

According to the researchers, their findings should be considered seriously by policymakers, as many of them apply to species known to have experienced decline in range and/or abundance as a consequence of intensive agricultural practices. Some experts, however, disagree with their contention. They assert: "It is possible that farmers who switched over to organic farming may have been predisposed towards ecofriendly methods. So the biodiversity on their farms may have been higher than average before the conversion."

The researchers assert that such criticism is unjustified, without 'rigorous and standardised' investigations between the differences between both the farming practices. They conclude by stating that further studies are essential to assess the capacity of organic conversion to reverse biodiversity losses.

Biodiversity