By growing several different types of crops at the same time – in other words, through intercropping – or by varying crop rotations, it is possible to enhance biodiversity. If the agricultural landscape consists of a variety of crops, this creates more habitats for wild plants and animals, which in turn can improve ecosystem services such as pollination and natural pest control.

Monotonous agricultural landscapes reduce the diversity of wild plants and animals

Over the years, Swedish agriculture has become more large-scale and efficient. This has led to agricultural landscapes becoming more homogeneous, with fewer crops, which in turn contributes to a decline in the biodiversity of wild plants and animals. One way to counteract this is to grow a wider variety of crops.

In this review, we have examined research on how crop diversity affects the diversity of wild plants and animals. The studies reviewed span different time periods and different scales within the agricultural landscape.

The analysis covers four types of crop diversity:

• Intercropping within a cultivated field during a given year
• Greater crop diversity in the agricultural landscape during a given year, i.e. mosaic-like landscapes
• More varied crop rotations within a cultivated field
• A more varied mosaic of crops in the agricultural landscape over time, i.e. the cultivation of different crops distributed across different fields over the years.

We have investigated what the science says about how biodiversity in the agricultural landscape is affected by a higher diversity of crops through intercropping, more varied crop rotations and a more varied mosaic of crops in the agricultural landscape. In addition, we have analysed data from Swedish agricultural landscapes to assess the potential for increasing crop diversity in Sweden.

We identified 158 research articles that could help answer these questions. Most of these studies addressed the effects of intercropping and varied crop rotations within a single cultivated field.

Growing different crops in the same field benefits the ecosystem

Increasing the number of crops in cultivated fields through intercropping and more varied crop rotations has a clear positive effect on biodiversity. When different crops are grown together or in succession, more habitats are created for wild plants and animals. This enables more species to establish themselves and survive. The effect is particularly evident for insects, decomposers and natural enemies of pests, which are given better conditions to contribute to ecosystem services, such as pollination. Data also shows that pest populations are declining, which is beneficial for crop production. Overall, the results demonstrate that increased crop diversity within cultivated fields is an effective measure for enhancing biodiversity whilst contributing to more sustainable agriculture.

Potential to increase biodiversity in Swedish agriculture

Analysis of Swedish cropping data shows that intercropping is uncommon in Sweden. It is practised on only a few per cent of arable land. There are also differences in the number and types of crops included in crop rotations across the country. Based on these findings, we see potential to increase biodiversity in Swedish agriculture by growing a greater variety of crops on the same field, particularly through the use of varied crop rotations.

The significance of the findings for work on environmental objectives

The findings are relevant to the environmental quality objectives A Rich Agricultural Landscape and A Rich Flora and Fauna. Increasing crop diversity can help to slow the loss of biodiversity and strengthen ecosystem services such as pollination and biological control. Mixed cropping has the greatest positive effect but is used to a limited extent in Sweden. This indicates a need for innovation and financial incentives to encourage more farmers to adopt the method. More varied crop rotations are easier to implement and yield clear positive effects. When it comes to growing different crops distributed across different fields within the agricultural landscape, there are too few studies to fully clarify the effects. It is therefore difficult to use this measure as a policy instrument to achieve environmental objectives.

Research needs

More studies are needed to investigate how a greater diversity of crops within an agricultural landscape affects wild plants and animals. More studies are also needed to investigate the impact on endangered species. Research should distinguish more clearly between the effects of intercropping and the effects of specific crops. It is also important to conduct studies that measure biodiversity at different levels, such as within fields and across entire agricultural landscapes, and that include functional and genetic diversity. This is necessary to understand the long-term consequences.