Long-term impacts of extensification of grassland management on biodiversity and productivity in upland areas. A review

Abstract

Modern rural policies that incorporate agricultural and environmental aims within the broader framework of sustainable rural development are being formulated to address the problem of declines in grassland biodiversity and the destruction of sensitive landscapes and habitats in Europe. Extensification is the process of reducing fertiliser inputs, management intensity and stocking rates, and is central to these sustainable rural policies. However, research in the Less Favoured Areas of Europe has been fragmented and highly variable reflecting the different uses and requirements of our upland areas. Information is needed to determine the nature and timescale of changes in such systems, and whether extensive management is sustainable in the long-term. This paper presents results from a range of grassland extensification experiments across Europe, mainly within the European Union, over the past 30 years that quantify the impacts on soil, plant and animal components of the system. All have the common theme of changing the focus of land management from solely the agricultural product to include a broader range of ecological and environmental objectives. Beneficial changes in biodiversity resulted from more extensive management treatments, but at the cost of reductions in total animal output, and in some cases a reduction in individual animal performance. However, it is clear that it is a long-term process to achieve many of these changes in biodiversity, and this must be recognised by policy makers. We recommend that future extensification studies adopt an approach that will allow their results to be applied throughout Europe.

How do sheep affect plant communities and arthropod populations in temperate grasslands?

“…This contrasts with the conclusions from surveys analyzing the effect of fertilizer cessation as an opportunity for restoring plant community diversity in fertile grasslands. Marriott et al (2004) and Tallowin et al (2005) found no great difference in the structure and composition between intensive grasslands and extensive grasslands that had been managed intensively in the past. High nutrient availability is indeed a major factor limiting the restoral of greater plant diversity in temperate grasslands (Janssens et al, 1998;Bakker and Berendse, 1999;Suding et al, 2005).…”

“…In upper alpine grasslands, stress-tolerant species, plants with low nutritive value and mosses declined after sheep exclusion (Mayer et al, 2009). In contrast to abandonment, reported changes in species composition were much slower when stocking rate was manipulated (Hulme et al, 1999;Marriott et al, 2004;Scimone et al, 2007). This was, for example, the case over the first 5 years of measurements in extensively used ryegrass/white clover sown swards (Marriott et al, 2002), although this last survey did find long-term patterns with A. capillaris, Poa trivialis, Festuca rubra and Holcus lanatus being favored by a reduction in stocking rate, whereas more competitive or ruderal species such as T. repens and Poa annua increased with increasing stocking rate (Marriott et al, 2009).…”

Effect of cattle grazing a species-rich mountain pasture under different stocking rates on the dynamics of diet selection and sward structure

“…Sward heterogeneity was systematically higher than that in plots grazed at a low stocking rate, with more than 15% of plot area kept at a reproductive stage at the end of the grazing season. This patch mosaic is expected to favour vegetation and insect diversity by providing resources for species characteristic of short as well as tall vegetation, with reduced disturbance for plant species that are less tolerant to grazing (Grime, 1979;Marriott et al, 2004), and increased habitat quality for insects requiring buffered microclimates (Wallis De Vries et al, 2007). Hence, it could represent the optimal balance to satisfy both livestock production and conservation management objectives.…”

“…This has been confirmed by surveys of changes in the botanical composition of pastures following a reduction of management intensity or stocking rates (e.g. Kiehl et al, 1996;Hart and Ashby, 1998;Marriott et al, 2004). However, a very low stocking rate is also assumed to reduce plant diversity as a result of competitive exclusion, where the high productivity of some species dominates plant species that cannot compete for light (Grime, 1979).…”

Grassland systems of red meat production: integration between biodiversity, plant nutrient utilisation, greenhouse gas emissions and meat nutritional quality

“…Additional nutrients are also applied to improved grassland in upland systems and, given the harsher growing conditions and shorter growing season in such areas, these applications are often crucial for maintaining overall system productivity. In line with this view, Fothergill et al (2001) and Marriott et al (2004) demonstrated substantial negative effects on sward carrying capacity and animal performance when such additional nutrients are withdrawn. The inputs of resources, and of N-fertilisers in particular, can be substantial and can result in a large N surplus, which is lost through leaching as nitrate or as gaseous N emissions.…”