Climate change accelerates the loss of biodiversity in agricultural ecosystems and cultural landscapes

Climate change is linked to the biodiversity of agricultural environments in many ways

Human activity and land use are the factors that affect the future of agricultural ecosystems the most. The indirect effects of climate change through the profitability of agriculture and adaptation measures relating to the timing of cultivation practices, such as tillage, the use of pesticides, and sowing and harvesting, are significant especially in the short term. Direct effects such as the lengthening of the growing season, the impact of increasing levels of carbon dioxide in the air on fertilisation, and the introduction of new species also affect the future of agricultural ecosystems [1]. Information about the effects of climate change on the ecosystem processes that maintain the biodiversity and productivity of agricultural ecosystems is still limited [2].

Important cultural biotopes are threatened by eutrophication and reforestation

Cereal crops and pastures that dominate in agricultural environments are often poor habitats for organisms. In agricultural environments, biodiversity is at its highest in cultural landscapes – landscapes shaped by traditional grazing and mowing regimes– such as meadows, dry grasslands, and wood pastures. They support a significant percentage of the species of insects, birds, and plants found in open landscapes. A total of 23% of the threatened species found in Finland occur in cultural landscapes and other environments shaped by humans, and they were the primary habitat for 37% of species that have already disappeared [3]. Due to structural changes in agriculture, cultural landscapes are at risk of abandonment and reforestation, and they are currently among the most threatened biotopes in Finland [4]. The indirect effects of climate change may cause cultural landscapes to deteriorate further [5].

As a result of the warm and rainy winters of the future, erosion and nutrient leaching in fields will increase considerably if cultivation practices are not revised. Without conservation tillage, a permanent cover of vegetation, or the introduction of winter cereal cultivars, nutrient leaching will increase, causing eutrophication in inland waterways and the Baltic Sea [1].

Eutrophication has already caused many biotopes to become threatened, and climate change will cause more and more coastal meadows to become colonised by reeds and increase the eutrophication of heathland as a result of flooding. The salinity of seawater and the wear caused by ice that prevents reforestation in coastal meadows are forecasted to decrease, which will increase eutrophication in coastal meadows. The gradual rise of the sea level also affects coastal meadows and wetlands. Finland has a major international responsibility to conserve coastal meadows unique to areas affected by post-glacial rebound [4], which is why efforts need to be made to mitigate the effects of climate change on them.

In addition to nutrient levels, the eutrophication and reforestation of cultural landscapes are accelerated by the lengthening of the growing season, the increasing levels of carbon dioxide in the air, and warmer temperatures. This may damage barren meadows and pastures, for example, which in turn may jeopardise the survival of many species that have adapted to open landscapes with little nutrients. Periodic dry spells in the summer may mitigate the effects of eutrophication in xeric habitats such as rock outcrops. As a result of eutrophication, cultural landscapes are likely to require more and more management such as mowing and grazing [5] [4].

Other changes in agricultural ecosystems

Warmer temperatures also bring new species to agricultural ecosystems. Changes are already visible as regards butterflies and birds, and the geographic ranges of many species have also spread northwards. The arrival of new species may increase the number of competitors, natural enemies, or diseases and therefore affect the number and abundance of species in agricultural environments and cultural landscapes. The increasing prevalence of plant diseases and pests may increase the need for chemical spraying, which increases the amount of toxins in surrounding ecosystems and depletes biodiversity [1].

There is uncertainty about changes in the ability of agricultural land to store carbon. The lengthening of the growing season and the warmer temperatures may increase carbon sequestration, but the amount of carbon released in the course of decomposition processes may also increase [1].