Daddy longlegs and an ecosystem under threat from climate change

Cranefly, which is more commonly known as daddy longlegs

Cranefly, which is more commonly known as daddy longlegs

31 July 2015

PhD research student Matthew Carroll, jointly of the Department of Biology, University of York and IBERS, Aberystwyth University is a key contributor to an article published in Nature Communications today.

Several rare upland bird species are being put at risk together with other ecosystem functions by the effects of climate change on the UK’s blanket bogs, ecologists at the University of York, Aberystwyth University and RSPB have discovered with the ecological research component on craneflies undertaken by Matthew and jointly supervised by Peter Dennis of Aberystwyth University.

Most of our drinking water comes from these upland peats and several iconic bird species such as the dunlin, golden plover and red grouse depend on these wetland habitats for nesting and feeding.

The scientists warn that climate change threatens these habitats, not only from rising temperatures increasing peat decomposition, but also via altered rainfall patterns – with summer droughts drastically affecting the blanket bog hydrology.

The study, which involved collaboration with the British Trust for Ornithology,  Aberystwyth University and the University of Leeds and part-funded by the RSPB, showed that the humble cranefly, more commonly known as ‘daddy longlegs’, is a crucial link in determining the impact of climate change on these peatland bird species.

The birds depend on the protein rich craneflies as food for chicks, but scientists have discovered that summer droughts, which are predicted to increase, will cause significant declines in craneflies numbers and subsequently the bird species that depend on them.

Dr Peter Dennis co-supervised Matthew Carroll’s PhD project and said “The benefits of a collaborative approach to research have been demonstrated in this Nature Communications article which has advanced our understanding of the consequences of climate change for the biodiversity and ecology of mountains, including those in Wales.”

Dr Dennis is a specialist in the ecology of uplands and mountains, whose research team has studied population changes of these keystone insect species in response to environmental changes and grazing management over many years in both the Scottish and Welsh hills.

The ecological research on craneflies by Matthew combined a model of water table depth of peat soils, produced by Andreas Heinemeyer of the Stockholm Institute, University of York, with information about the numbers of craneflies recorded in wetter and drier areas of peatland, recorded by Matthew in his detailed field studies of these insects across peatlands, known as blanket bogs.

Craneflies (both the daddy long leg adults and leatherjacket larvae) thrive in wet, peat soils and their density is shown to fall and geographic distribution diminish under the warmer, drier scenario of summer droughts, according to the simulation model based on real population data from upland study sites.

The three experimental sites included one in the Berwyn Hills that form the watershed of Lake Vyrnwy in Wales, under RSPB management. The simulation model was extended to predators of the cranefly and showed a detrimental effect on the numbers of bird species of the uplands, including golden plover and dunlin, since the insects are a significant part of the diet of these birds, especially during the breeding season from May each year.

The collaboration with lead NERC supervisor Prof Chris Thomas, University of York and James Pearce-Higgins, formerly of the RSPB, was made possible by Welsh Government funding via a Research and Enterprise Partnership between Aberystwyth University and Bangor University (the “Centre for Integrated Research in the Rural Environment”).

The research suggests that large-scale projects to restore degraded and eroded blanket bogs could be critical in securing the future of these internationally important bird populations, alongside both water supplies and the crucial role of blanket bogs as a carbon store.

Dr Dennis concluded: “The combination of efforts across several research specialisms has provided insight into the possible outcome of climate change, should this translate to generally drier and warmer summers in the mountains of Wales and elsewhere in the UK.”