Reconciling ecology and economics to conserve bumblebees

Abstract

Many bumblebee species have experienced severe population declines in response to the use of intensive land management practices throughout the UK and western Europe during the latter half of the twentieth century. The loss of wildflower-rich unimproved lowland grasslands has been particularly detrimental and, as a result, in the UK two bumblebee species are now extinct, seven are listed on the UK Biodiversity Action Plan (BAP), and only six extant species remain common and ubiquitous. Populations of the rarer species are often fragmented and restricted to isolated areas, such as the crofting regions of northwest Scotland, in which the use of intensive farming practices has remained relatively limited. Consequently, in this study I primarily focus on the conservation of B. distinguendus and B. muscorum, two of the UK’s rarest species which have strongholds in the Outer Hebrides. In this region crofting is the dominant form of agriculture, and is traditionally typified by small-scale mixed livestock production accompanied by rotational cropping activities. With the use of very few artificial inputs, traditional crofting activities are environmentally sensitive and promote the diverse wildflower assemblages characteristic of the machair which provide suitable forage for bumblebees. However, the changing demographic structure of the islands, in conjunction with a range of other socio-economic factors, is resulting in the adoption of more intensive land management practices by crofters and changing the nature of the crofted landscape. These changes are likely to have a detrimental impact on the rare bumblebee populations that rely on crofting to provide suitable foraging habitats. Neglecting to examine the socio-economic issues behind the decline in crofting activities, and failure to develop a means of making the system economically viable and sustainable, is likely to reduce the effectiveness of any bumblebee conservation measures introduced in the region. Through my research I address this socio-ecological problem by taking an interdisciplinary approach, and combine the two disciplines of ecology and economics to find a way to ensure crofting is sustainable whilst promoting sympathetic land management practices to aid bumblebee conservation. The results of my research demonstrate that current croft land management practices do not support high abundances of foraging bumblebees in the Outer Hebrides, and that sheep grazing during the summer has a particularly negative impact on bumblebee abundance on croft land. My research also highlights the importance of non-agricultural habitats for foraging long-tongued bumblebee species in agricultural landscapes. Grazing management can promote bumblebee abundance, with cattle grazing providing a valuable foraging habitat for short-tongued bumblebees in southwest England. Therefore, to conserve bumblebees in agricultural landscapes the type of farming system needs to be taken into account in developing grazing management regimes, whilst non-agricultural habitats need to be integrated into local land management plans to ensure the provision of forage for bumblebees throughout the flight period. The outputs of the ecological-economic models show that compensation payments are not always required to encourage beneficial land management practices to enhance bumblebee populations in crofted areas. However, crofting is a marginal farming system that is heavily influenced by socio-economic factors, and this should be taken into consideration in the development of future agricultural policy for the region.