Impact of woodland agri-environment management on woodland structure and target bird species
Author(s): Bellamy, P.E., Charman, E.C., Riddle, N., Kirby, W.B., Broome, A.C., Siriwardena, G.M., Grice, P.V., Peach, W.J. & Gregory, R.D.
Published: May 2022
Journal: Journal of Environmental Management Volume: 316
Article No.: 115221
Digital Identifier No. (DOI): /10.1016/j.jenvman.2022.115221
Woodland bird communities are strongly influenced by woodland structure, which also determines the habitat suitability for individual species. The structure of UK woodlands has changed significantly. Much native woodland had been intensively managed for centuries (e.g. as coppice) to deliver a range of products, but such management practices had been largely abandoned by the middle of the 20th century. Since then, much of this woodland has reverted to closed canopy forest. Alongside this, other changes have been driven by increasing deer populations, climate change, and shifting approaches to woodland management, all of which have been linked to declines in the populations of many woodland bird species.
Agri-environment schemes have provided funding to support biodiversity conservation on both farmland and (to a lesser extent) woodland. Within England, Woodland Improvement and Woodland Management Grants have been used to improve public access, to restore native woodland and to improve the condition of protected sites. Such grants have also been used to create specific options that support regional priorities, including woodland bird populations. One such initiative, deployed in the East Midlands and called the East Midlands Woodland Bird Project, set out to improve the structure of predominantly broadleaved woodland for a suite of specialist woodland bird species. The scheme, which was a collaboration between the Forestry Commission and the RSPB, was started in 2007 and took funding applications from 2009 to 2015.
Baseline monitoring was used to establish the effectiveness of delivering land management incentives in this way, and this paper sets out to determine whether the scheme has delivered the intended changes in woodland structure, and enhanced the abundance of the target bird species. The abundance of breeding birds (using two methods: point counts and territory mapping) and metrics of woodland structure were recorded on sites with Woodland Improvement Grants (improvement sites) and nearby comparison sites (control sites). Initial measurements were made prior to management and repeated seven to nine years later. A separate comparison of changes in bird abundance was made between the managed woodland sites and woodland from similar landscapes surveyed as part of the national BTO/JNCC/RSPB Breeding Bird Survey (BBS).
There was an increase in the abundance of target species on improvement sites compared to a decrease on both control sites and BBS sites, although this was only evident from point count data. The effects on target species were stronger than for other woodland specialists and there was no apparent effect on woodland generalists, suggesting that the management interventions were appropriate for the target species. Changes in woodland structure were generally consistent with the expected effect of management, with lower tree density and greater Bramble (Rubus sp.) cover. However, contrary to the aim of increasing understorey cover, a reduction was recorded within the 2–10 m height category in improvement sites. This contrast is due to the removal of young trees during thinning affecting this height band and the short time since management to allow regrowth.
The study highlights that bespoke woodland management, supported through agri-environment incentives, can have a positive impact on target woodland bird populations. Securing the right approach is dependent upon understanding the habitat requirements of the target species, but it does underline that the use of targeted funding support can deliver biodiversity gains and achieve policy goals.