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Changes in farming practices over the past century have had negative influence on farmland biodiversity. Organic farming excludes most agrochemicals, such as inorganic fertilisers and synthetic pesticides, and can be an alternative to conventional farming. A recent meta‐analysis indicates that there is on average 30% higher species richness on organically managed farmland compared to conventionally managed farmland. There are, however, large variation between organism groups, with a positive influence on plants and pollinators and possibly predators and birds, but less influence on and insufficient knowledge for other groups. Using more formal experimental design, focusing on understudied organism groups and aspects of biodiversity, such as genetic and ecosystem diversity, and evaluating effects on rare species would advance our knowledge. The yield reduction under organic farming, resulting in more land needed to produce the same amount, could offset some of the biodiversity benefits of organic farming.
Organic agriculture is a production system that aims at sustaining healthy soils, ecosystems and people by prohibiting the application of synthetic pesticides and fertilisers in crop production and by emphasising animal welfare in livestock breeding. This article shows that organic agriculture is characterised by higher soil quality and reduced nutrient or pesticide leaching compared to nonorganic agriculture, but that positive effects on biological control services or emission of greenhouse gases are less evident. Yield gaps between organic and nonorganic agriculture are on average 20%, but vary between crops and regions. Given the environmental risks that are associated with intensive, nonorganic agriculture, farming practices should be modified to decrease risks. Organic agriculture can be a more environmentally friendly alternative, but individual farming practices need improvement to meet the demands of a growing human population. Further growth of the organic farming sector will contribute to reduce the negative environmental impact of agriculture.
Crop diversity benefits carabid and pollinator communities in landscapes with semi‐natural habitats
(2020)
1.In agricultural landscapes, arthropods provide essential ecosystem services such as biological pest control and pollination. Intensified crop management practices and homogenization of landscapes have led to declines among such organisms. Semi‐natural habitats, associated with high numbers of these organisms, are increasingly lost from agricultural landscapes but diversification by increasing crop diversity has been proposed as a way to reverse observed arthropod declines and thus restore ecosystem services. However, whether or not an increase in the diversity of crop types within a landscape promotes diversity and abundances of pollinating and predaceous arthropods, and how semi‐natural habitats might modify this relationship, are not well understood.
2. To test how crop diversity and the proportion of semi‐natural habitats within a landscape are related to the diversity and abundance of beneficial arthropod communities, we collected primary data from seven studies focusing on natural enemies (carabids and spiders) and pollinators (bees and hoverflies) from 154 crop fields in Southern Sweden between 2007 and 2017.
3. Crop diversity within a 1‐km radius around each field was positively related to the Shannon diversity index of carabid and pollinator communities in landscapes rich in semi‐natural habitats. Abundances were mainly affected by the proportion of semi‐natural habitats in the landscape, with decreasing carabid and increasing pollinator numbers as the proportion of this habitat type increased. Spiders showed no response to either crop diversity or the proportion of semi‐natural habitats.
4. Synthesis and applications. We show that the joint effort of preserving semi‐natural habitats and promoting crop diversity in agricultural landscapes is necessary to enhance communities of natural enemies and pollinators. Our results suggest that increasing the diversity of crop types can contribute to the conservation of service‐providing arthropod communities, particularly if the diversification of crops targets complex landscapes with a high proportion of semi‐natural habitats.