More than a third of the earth’s land area is currently used for agricultural production, which has resulted in a dramatic decrease of natural habitats. Combined with intensive agriculture, this has led to a reduction in the number of individuals and species of wildlife. With an ever-increasing demand for crops from a growing population the need for methods to reduce the negative effects of agriculture on biodiversity is greater than ever.
This according to William Sidemo Holm, who recently defended his dissertation ”Effective conservation of biodiversity and ecosystem services in agricultural landscapes” at Center for Environmental and Climate Science (CEC). He has specifically studied how existing measures, such as the establishment of buffer strips as well as organic farming, can be implemented to have a greater effect on biodiversity.
”There are many ways to promote biodiversity in agricultural landscapes, but the efficiency depends on where and how they are carried out. Furthermore, since these methods often give rise to increased costs for farmers, it is important that they are carried out cost-effectively”, says William Sidemo Holm.
Biodiversity maximises profit
The majority of environmental payment that farmers can receive today are action-based. This means that the size of the compensation is calculated based on the type of measure and its scope. The effect of the action is not taken into account when estimating the payment size. According to William Sidemo Holm, this provides an economic incentive for farmers to place buffer strips – strips of vegetation that are left unused – on the part of the land that is least profitable and not on the land where the action would have had the greatest effect. This because it reduces the lost income. As an alternative, William Sidemo Holm has looked at what effects result-based payments would have on both the farmers and biodiversity. Result-based payments means that the farmer gets payed based on the effects of the measure.
However, there is a problem with result-based payments and that is how to measure the results. This may, for example, apply to measures to reduce nutrient leakage, such as buffer strips. But by using models that applied different landscape variables (for example soil type, slope and crop type), William Sidemo Holm could calculate the nutrient runoff and estimate the effects of the buffer stripes.
”If a farmer places buffer strips where they will have best chance to maximise the profit, the environmental impact on biodiversity will be seven times higher compared to if the compensation is action-based. This is because the farmer gets an incentive to place the strips where they have most environmental benefits instead of putting them where they lead to the lowest foregone income”.
Increased distance between crops benefits biodiversity
Besides investigating the effects of buffer strips he also looked at effects of organic farming on biodiversity. His study showed that even though organic yields are smaller, these fields have significantly greater richness in species. However, the correlation was only apparent when the yields were small.
”I didn’t expect that the positive effect of organic farming would disappear when harvests went up. This is probably because the methods used to increase the harvests have a negative effect on flowering weeds”, he says.
This could become a problem as organic farmers try to increase their yields. As a small comfort however, he also found that the problem could be partially avoided by increasing the distance between the crops to benefit flowering weeds.
"The result shows that by increasing the distance between crops in the same row from five to ten centimeters, flower diversity is doubled, without having any apparent effect on the harvest."
Hoping to make a change
William Sidemo Holm hopes that the results from these and other studies in his thesis will contribute to policymaking that enable both higher biodiversity and profitable agricultural production.
"These studies have clearly shown that there is a benefit in redoing compensation schemes for various environmental measures so that they are used where they have the greatest ecological impact given the cost."