8 april 2009

Hedgerow trees ‘key to UK biodiversity’

Science

Garden Tiger [Arctia caja]
Garden Tiger moth [Arctia caja] – has seen an 89 per cent decline in last 35 years. Credit: Maarten Jacobs.

Paying farmers to protect and establish more hedgerow trees could be crucial to halting the decline in biodiversity in the British landscape, Oxford University scientists have found.

The team focused on larger moths – many of them spectacularly beautiful – as an important indicator of biodiversity, recording the number and diversity of 270 species of moths on 16 arable farms across Oxfordshire. 

What they found was that whilst wide field margins – for which farmers are already financially rewarded – are beneficial for moth populations, hedgerow trees had an even greater impact: in some landscapes boosting moth numbers by 60 per cent and their species diversity by 38 per cent. 

A report of the research appears in the April edition of the journal Agriculture, Ecosystems and Environment.

Our results suggest that the shelter provided by hedgerow trees is probably the main reason for their beneficial effects on moth numbers and diversity ‘Our results suggest that the shelter provided by hedgerow trees is probably the main reason for their beneficial effects on moth numbers and diversity,’ said Dr Thomas Merckx of Oxford University’s Wildlife Conservation Research Unit (the WildCRU) the lead author of the report.

Our results suggest that the shelter provided by hedgerow trees is probably the main reason for their beneficial effects on moth numbers and diversity.

Dr Thomas Merckx

‘They create a sheltered microclimate for individual moths and may act as ‘stepping stones’ enabling moths and other insects to cross open agricultural spaces. This could make hedgerow trees even more important in the future for British and European biodiversity, since they may mitigate some negative effects of climate change by allowing species to move northwards in response to climate change, even through agricultural landscapes.’

Currently the restoration and management of wide field margins is financially rewarded in the EU but there are no such incentives for farmers to manage hedgerow trees. 

Dr Merckx said: ‘What our research shows is that, if we are to preserve the biodiversity of agricultural landscapes in Britian and Europe, we have to think bigger than measures relating to individual fields and individual species, and examine what we can do to strengthen the diversity within landscapes and ecosystems as a whole.’ 

Professor David Macdonald, founding Director of the WildCRU, who led the Oxford University team that collaborated with the charity Butterfly Conservation, said: ‘We got the best results where we targeted farmers to join agri-environment schemes, probably because this resulted in the joining up of good habitat across the landscape.’

Professor Macdonald added, ‘nowadays, the taxpayer pays farmers as custodians of biodiversity in the countryside. It’s important that these agri-environment payments deliver the sort of countryside that the public wants, and our research is intended to provide the evidence policy-makers need.’

The research was funded by the Esmee Fairbairn Foundation, and is part of the WildCRU’s wider programme of studying how to conserve wildlife on farms in the Upper Thames Valley, research which spans water voles to otters, damsel flies to badgers and harvest mice to fish. 

Professor Macdonald said: ‘With the moth results in hand, our next step is to test the effects on the bats that feed on them – the idea of the Upper Thames project is to explore links between farming and the whole food web on farmland.’