Sustainability Issue #4 August 2010

Recent studies from the UK show that the difference in biodiversity between organic and conventional farms, measured as the number of species, is relatively small. Diversity is 12 per cent higher on organic farms. There are large differences between harvests – an organic harvest is one half that on a
conventional farm. In a press release the authors therefore claim that organic farming is a luxury that we will not be able to afford when the production of food must be doubled within 40 years to cater for the world's population.

In order to preserve organic farming cost effectively, organic farming should therefore be concentrated in areas where the differences between organic and conventional farming is small. In Sweden we have shown, on the other hand, that organic farming has a greater effect on biodiversity in more intensively farmed areas where biotopes similar to natural ones are largely absent.

In  turn, a German study claims that environmental support such as subsidies for organic farming should be directed towards intermediate areas, i.e. towards neither highly intensive nor highly extensive farming.

These contrasting studies illustrate the dilemma faced by decision makers; how environmental support such as subsidies for organic farming should be designed so as to preserve or increase biodiversity in a cost effective way.  In order that the right decision may be made, there must be data available to show how biodiversity is affected by the way farming is carried out, but there must also be a clear objective to preserve biodiversity.

Few evaluations

The aim of the Swedish environmental objectives, such as "A varied agricultural landscape" and "A rich diversity of plant and animal life" is to preserve biodiversity in the agricultural landscape. In order to provide incentives for European farmers to reduce their environmental load and increase their positive contributions to biodiversity, there is a system of environmental subsidies. Each EU member country is free to formulate its own support programme. Although these programmes spend quite large sums of money, there are few proper evaluations of whether the invested money really has the intended effect.

The difficulties in making an evaluation is that in many cases there are no initial values of what biodiversity had been like before a certain measure was embarked upon. Another difficulty is that the environmental subsidies have several different objectives, all from cultural to biological, and that these are sometimes in conflict. Scientific evaluations so far show that many of the measures that are stimulated by these subsidies have no demonstrable effect on biodiversity. When the Swedish rural programme was evaluated, it was found that the measures had often been taken on valuable land, but that biodiversity nevertheless cannot be evaluated owing to lack of data.

Beer of the future? In order that the right decision may be made, there must be data available concerning biodiversity in farming. And also clear objectives. The photograph is that of a conventionally farmed field. But the edges have not been sprayed, and that may be one reason that the cornflower has spread. Photographer: Georg Andersson.

Less biodiversity in intensive farming

Organic research shows quite clearly that it is intensification of agriculture that has caused biodiversity to decrease. One of the ways this has come about is the creation of landscapes that are more homogeneous on different spatial scales. Examples of intensification are the change from hay to silage, the increased use of chemical control agents and commercial fertilisers, and the large scale structural rationalisation that has taken place in farming.

A large European study has recently shown that species diversity among plants, ground beetles and birds has diminished as a result of the intensification of agriculture. It was primarily control agents against insects and fungi that were shown to have a large negative effect on biodiversity. Intensification will probably increase in future as there is a greater need for agricultural products for an increasing population and a greater need for bioenergy.

Species rich. The photographer is a researcher and has marked the object of his study, Pterostichus melanarius, for a mark-recapture experiment to see how ground beetles spread. Photographer: Erkki Palmu.

Difficult to determine value

In  order to effectively preserve biodiversity in the agricultural landscape, we must decide why and where we want to preserve diversity. Sweden has ratified the convention on biodiversity and has therefore undertaken to preserve the species that are extant in the country. This has been incorporated in the Swedish environmental objectives. Since the Swedish red list shows that many threatened organisms are associated with the agricultural landscape, there is a need for measures in these landscapes that will result in the continued existence of rare species populations.

In order to preserve rare species in an effective way, the reasoning put forward in the above UK study may be correct. By focusing measures on areas and landscapes where biodiversity is already high and where the cost of these measures is relatively low, high cost effectiveness can be achieved. But this does not result in higher diversity in the intensively farmed areas. Need we preserve and increase diversity in these areas also? Biodiversity is needed for the retention of many ecosystem services which humans make use of. The Millenium Ecosystem Assessment divides these into provisioning functions such as food and water, regulating functions such as flood and disease regulation, cultural functions such as spiritual and recreational perceptions, and supporting services such as nutrient and water cycling.

A tree that gives shade also performs an ecosystem service for us, since the need to cool the air by human technology is reduced. It is therefore also possible to assign a value to this service by finding what it would have cost to cool the air by technology. The monetary value of ecosystem services is large but difficult to estimate since it depends on assumptions regarding factors such as the rate of discount.

Makes money. The bee as a pollinator provides ecosystem services for humans. Here on common tansy. Photographer: Georg Andersson

Test on rape. Researchers at Lund University have set out bee communities to compare biodiversity in different types of biotopes. Both domesticated and wild pollinators can positively affect the yield of agricultural crops. Photographer: Maj Rundlöf.

Valuable shade. A tree gives us a number of ecosystem services. To measure what it costs to cool the air with human technology instead of using the shade of the tree is difficult, but it can be done. This tree is in Ekoparken, a green wedge with biodiversity that runs through Stockholm. Photographer: Magnus Kristenson.

A rare sight. It is seldom that storks can be seen in the Swedish agricultural landscape, which is mostly due to the large scale ditching. Photographer: Ola Olsson.

Changes are affected

Earlier studies tried to estimate the total value of ecosystem services, but from an economic standpoint it is often of interest to wonder how a change affects the value of ecosystem services. In this context, a study of a change to organic farming may be of interest.

Many other values, such as the aesthetic ones, are however difficult to value in monetary terms.

The loss of biodiversity threatens ecosystem services in the farming landscape, but very little is known at present of what the strength and the form of the relationship are like between diversity and ecosystem services. It has also been argued that biodiversity could act as a buffer or assurance that in a changing world there is always some species that can perform the services we need.

If biodiversity is of key importance for the retention of ecosystem services in a changing world, it is vital that biodiversity should be preserved not only on a national scale but in all agricultural landscapes, regardless of whether they are intensively and extensively cultivated.

Pollination and control of insect pests

Control of insect pests is part of the ecosystem services produced on the farm. One example is a ladybird eating an aphid. Another ecosystem service is nitrogen fixation which is the bacterial work performed in symbiosis with legumes, and naturally with the ability of the wheat plant to convert nutrients and sunlight into a protein-rich nucleus. It is thus both the domesticated and wild biodiversity that produce ecosystem services.

It must however be pointed out that research on organic farming and ecosystem services is still in its infancy. The services which have so far received most attention in research are pollination and the control of insect pests.

In Nordic agriculture it is the wind pollinated crops that are dominant, but the harvests of our oil plants can increase by 5 - 15 per cent thanks to good pollination. Pollination can therefore be given a value. On coffee plantations in Costa Rica the harvest and quality of the coffee were higher in the vicinity of natural forests. This was a result of good pollination and contributed 60,000 dollars annually to the study farm.

The honey bees which travel enormous distances in the US are fundamentally different from the natural pollinators. In the US, for many beekeepers the pollination service is more important than the honey produced. It must however be emphasised that on organic farms with natural environments the pollination of a crop with a high pollination requirement - water melon - was satisfactory only because of the wild pollinator fauna, while on intensive agricultural areas the honey bee was needed for a satisfactory harvest. This is especially important these days when such bees are affected by Colony Collapse Disorder.

When pests are controlled in greenhouses, this is often done by setting out “communities” of various small predators - parasites or parasitoids. But out on the fields reliance is placed on the natural enemies of the pests or on chemical methods. It has been found that aphids become established to a lower degree on organic farms and on farms in heterogeneous landscapes, since on these more aphids are eaten by their natural predators. Thanks to such predation, harvest loss was reduced by about 300 kg per hectare. Biodiversity in the farming landscape can favour both pollination and the control of insect pests, which may, in turn, improve the economy of the farmer.

What should be prioritised?

What must the farming landscape deliver? This is a choice that must be made locally by the farmer, but also regionally and nationally by society. How we should assign priorities depends on what value we place on biodiversity as such. It is a matter of putting the main emphasis on preserving unusual species, or ensuring that usual species will not become unusual, but also of how we value ecosystem services.

Many of the services produced in the agricultural landscape are to the benefit of  society as a whole and not only the farmer. It is therefore essential to combine ecological knowledge and the will and needs of society in different interdisciplinary collaborations and arenas in order to be able to decide how the payments to farmers for the production of ecosystem services should be formulated.

Organic farming, the environmental subsidies for which have received the most study, has generally a positive effect on biodiversity and probably also on ecosystem services. This effect depends on where in the landscape organic farming is carried on. In order that we may be able to answer the question where organic farming should be located in the landscape, more research is needed on biodiversity, ecosystem services, the attitude of farmers to organic farming, and the cost of a change to organic farming. All these choices must take account of landscape effects and relationships.

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