Effective conservation of biodiversity and ecosystem services in agricultural landscapes
Abstract: Agricultural land use is a major driver of biodiversity losses and changes in ecosystem services. Thus, for the sake of both humans and wild organism per se, effective strategies that enable both agricultural production and conservation of biodiversity and ecosystem services are urgently needed. Such strategies can be divided into those that reduce the intensity of farming in general (such as organic farming), and those that target specific habitats of key importance for farmland biodiversity (e.g., maintaining semi-natural, grazed grasslands). In this thesis, I used a combination of scientific methods in five different studies to assess and propose such strategies that promote biodiversity and ecosystem services, effectively and cost-effectively, in agricultural landscapes. This included reviewing the literature on land-sharing vs. land-sparing strategies, which explicitly compare the merits of spatially integrating (land sharing) or separating (land sparing) biodiversity conservation and agricultural production, respectively. I found that the literature has focused on a limited number of taxonomic groups, ecosystem services and economic factors (particularly birds, carbon storage and agricultural output), which impedes a more holistic understanding of the strategies’ social and ecological consequences. In another study, I evaluated the potential of organic farming to preserve rare species, which includes species of high conservation concern. Using a meta-analysis on a global dataset, I showed that organic compared to conventional farming benefits both rare and common species of arthropods, birds, earthworms and plants. I also carried out an empirical study where I compared abundance and diversity of bumblebees and flowering weeds, as well as crop yields, across 19 organic and conventional farms. The study showed that organic farming benefits bumblebees by harboring more flowering weeds, but only when crop yields are low. This demonstrates the need for strategies to enhance yields in organic crop fields (which are typically lower than those in conventional fields) without degrading the benefits of organic farming to biodiversity. I found that one such strategy can be to reduce crop sowing density, which benefited flowering weeds and thus indirectly bumblebees, without significantly affecting crop yields. I subsequently used data from the same farms in a study where I modelled the influence of landscape complexity on the cost-effectiveness of organic farming in promoting plant species richness. The cost- effectiveness, in terms of achieving targets for increasing species richness at a landscape scale at the lowest possible cost, was highest in the least complex landscape. Lastly, I performed a study showing how a model can be used to predict environmental results in result-based payment schemes. The study demonstrated that result- based payments can promote substantially more cost-effective agricultural pollution abatement than action- based payments. In conclusion, this thesis has contributed with new knowledge about how existing conservation strategies affect biodiversity and ecosystem services, as well as proposed novel conservation strategies. The findings of this thesis can contribute to more effective and cost-effective conservation and promotion of biodiversity and ecosystem services in agricultural landscapes.
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