Johan Ahnström

Land‐use intensity and the effects of organic farming on biodiversity: a hierarchical meta‐analysis

Summary The benefits of organic farming to biodiversity in agricultural landscapes continue to be hotly debated, emphasizing the importance of precisely quantifying the effect of organic vs. conventional farming. We conducted an updated hierarchical meta‐analysis of studies that compared biodiversity under organic and conventional farming methods, measured as species richness. We calculated effect sizes for 184 observations garnered from 94 studies, and for each study, we obtained three standardized measures reflecting land‐use intensity. We investigated the stability of effect sizes through time, publication bias due to the ‘file drawer’ problem, and consider whether the current literature is representative of global organic farming patterns. On average, organic farming increased species richness by about 30%. This result has been robust over the last 30 years of published studies and shows no sign of diminishing. Organic farming had a greater effect on biodiversity as the percentage of the landscape consisting of arable fields increased, that is, it is higher in intensively farmed regions. The average effect size and the response to agricultural intensification depend on taxonomic group, functional group and crop type. There is some evidence for publication bias in the literature; however, our results are robust to its impact. Current studies are heavily biased towards northern and western Europe and North America, while other regions with large areas of organic farming remain poorly investigated. Synthesis and applications. Our analysis affirms that organic farming has large positive effects on biodiversity compared with conventional farming, but that the effect size varies with the organism group and crop studied, and is greater in landscapes with higher land‐use intensity. Decisions about where to site organic farms to maximize biodiversity will, however, depend on the costs as well as the potential benefits. Current studies have been heavily biased towards agricultural systems in the developed world. We recommend that future studies pay greater attention to other regions, in particular, areas with tropical, subtropical and Mediterranean climates, in which very few studies have been conducted.

Farmers and nature conservation: What is known about attitudes, context factors and actions affecting conservation?

Farmers’ attitudes towards viability of specific conservation practices or actions strongly impact their decisions on adoption and change. This review of ‘attitude’ information reveals a wide range of perceptions about what conservation means and what the impacts of adoption will mean in economic and environmental terms. Farmers operate in a tight financial situation, and in parts of the world they are highly dependent on government subsidies, and cannot afford to risk losing that support. Use of conservation practices is most effective when these are understood in the context of the individual farm, and decisions are rooted in land and resource stewardship and long-term concerns about health of the farm and the soil. The attitudes of farmers entering agri-environmental schemes decide the quality of the result. A model is developed to show how attitudes of the farmer, the farming context and agri-environmental schemes interact and thus influence how the farming community affects nature and biodiversity. As new agri-environmental schemes are planned, agricultural development specialists need to recognize the complexity of farmer attitudes, the importance of location and individual farmer circumstances, and the multiple factors that influence decisions. We provide these insights and the model to conservation biologists conducting research in farming areas, decision makers who develop future agri-environmental schemes, educators training tomorrow’s extension officers and nature conservationists, and researchers dealing with nature conservation issues through a combination of scientific disciplines.

Effects of organic farming on biodiversity and ecosystem services: taking landscape complexity into account

The recent intensification of the arable landscape by modern agriculture has had negative effects on biodiversity. Organic farming has been introduced to mitigate negative effects, but is organic farming beneficial to biodiversity? In this review, we summarize recent research on the effects of organic farming on arable biodiversity of plants, arthropods, soil biota, birds, and mammals. The ecosystem services of pollination, biological control, seed predation, and decomposition are also included in this review. So far, organic farming seems to enhance the species richness and abundance of many common taxa, but its effects are often species specific and trait or context dependant. The landscape surrounding the focal field or farm also seems to be important. Landscape either enhances or reduces the positive effects of organic farming or acts via interactions where the surrounding landscape affects biodiversity or ecosystem services differently on organic and conventional farms. Finally, we discuss some of the potential mechanisms behind these results and how organic farming may develop in the future to increase its potential for sustaining biodiversity and associated ecosystem services.

Local selling as a driving force for increased on-farm biodiversity

This paper addresses the question of whether local selling of farm products improves on-farm biodiversity in rural areas. In contrast to the main agricultural trend of farms specializing and increasing in size in response to national and global markets, increasing numbers of Swedish farmers are diverting their efforts towards selling at local markets. Based on case studies of six farms selling their products locally, this paper explores the nature of the diversity on these farms and identifies qualities in the interaction between the farmers and their consumers that are supporting this diversity. The study showed that farmers who interacted with consumers were encouraged to diversify their production. Marketing a large diversity of products at a local market led to better income for participating farmers. Animal farms maintained important biodiversity associated with their extensive way of rearing animals on semi-natural pastures. Access to local markets promoted this.

Essential multiple functions of farms in rural communities and landscapes

As farms are consolidated into larger operations and small farms close down for economic reasons, rural areas lose ecological, social and economic functions related to farming. Biodiversity and scenic, open-vista landscapes are lost as fields are left unmanaged. Social and economic benefits such as local job opportunities and meeting places disappear. Four Swedish rural communities were examined to increase our understanding of the functions that a diverse agriculture provides and which of these are lost as farms cease operation and overall rural social capital is depleted. Workshops and interviews with village action groups and with farmers were carried out. Both groups identified key functions from farming that are important to the rural community, such as production of food and fiber, businesses and jobs, human services, local security, ecosystem services such as nutrient cycling and biodiversity, and functions pertaining to quality of life. Several ways in which village action groups can support agriculture were identified that current industrial agriculture and even agri-environmental schemes fail to achieve. These include organizing local meeting places, encouraging local processing and consumption and supporting farmers in their work. We conclude that agriculture and village action groups match well in community development and that policies supporting this match would be useful.

Farmers' Interest in Nature and Its Relation to Biodiversity in Arable Fields

Biodiversity declines in farmland have been attributed to intensification of farming at the field level and loss of heterogeneity at the landscape level. However, farmers are not solely optimizing ...

Different patterns in species richness and community composition between trees, plants and epiphytic lichens in semi-natural pastures under agri-environment schemes

Agri-environment schemes (AES) have been established to counteract negative effects of agricultural intensification on e.g. semi-natural pastures and meadows. The efficiency of most AESs have, however, been poorly evaluated. We evaluated the success of a Swedish AES for the management of semi-natural pastures by comparing species richness and composition of vascular plants (except trees), epiphytic lichens and trees among pastures receiving higher (high value pastures) and lower levels of AES paymens (general value pastures). There was no difference in the number of tree species among high and general value pastures, even though AES regulations allow a maximum of 60 and 100 trees/ha in general and high value pastures, respectively. High value pastures had, however, a higher number of plant and epiphytic lichen species than common value pastures. Moreover, a higher number of pasture specialist plant species were indicative of high value pastures than of general value pastures. No lichen species indicating high value pastures are associated with habitats with low canopy cover (such as e.g. pastures). Finally, tree identity was an important factor for explaining the number and composition of epiphytic lichen species. Our study highlights that species groups can respond differently to agri-environment schemes and other conservation measures. Even though the effects are the desired on the diversity of one assessed taxon, this is not always the case for non-target organism groups.