A counterfactual approach to measure the impact of wet grassland conservation on U.K. breeding bird populations

Abstract

Wet grassland populations of wading birds in the United Kingdom have declined severely since 1990. To help mitigate these declines, the Royal Society for the Protection of Birds has restored and managed lowland wet grassland nature reserves to benefit these and other species. However, the impact of these reserves on bird population trends has not been evaluated experimentally due to a lack of control populations. We compared population trends from 1994 to 2018 among 5 bird species of conservation concern that breed on these nature reserves with counterfactual trends created from matched breeding bird survey observations. We compared reserve trends with 3 different counterfactuals based on different scenarios of how reserve populations could have developed in the absence of conservation. Effects of conservation interventions were positive for all 4 targeted wading bird species: Lapwing (Vanellus vanellus), Redshank (Tringa totanus), Curlew (Numenius arquata), and Snipe (Gallinago gallinago). There was no positive effect of conservation interventions on reserves for the passerine, Yellow Wagtail (Motacilla flava). Our approach using monitoring data to produce valid counterfactual controls is a broadly applicable method allowing large‐scale evaluation of conservation impact.

Do conservation designations provide positive benefits for bird species and communities?

“…The effects were strongest for SPAs, that is areas specifically designated under European legislation for protecting birds, particularly rarer and declining habitat specialists. This supports the results of continent-wide associations (Donald et al 2007), and previous single-species analyses (Franks et al 2018, Jellesmark et al 2021. Importantly, the effects we found were present despite wide variation in the intensity of site management of the PA (Starnes et al 2021), which we did not account for.…”

“…Thus, those species with the most positive effects of PA on their status and trend also show higher rates of breeding success in PA. There is growing evidence in support of management interventions being effective in boosting the breeding success of birds of conservation concern (Franks et al 2018, Pearce-Higgins et al 2019, contributing to positive associations between those species and protected areas (Gillingham et al 2015, Franks et al 2018, Jellesmark et al 2021, and the potential to stem or reverse species declines more generally (Morrison et al 2021). The lack a positive relationship between productivity and PA extent and abundance trend across species (Table S3), suggests either that PA are not associated with greater habitat quality (and many are in 'unfavourable' condition, Starnes et al 2021) or, given that they tend to be associated with greater rates of occurrence and higher abundance, there may be densitydependent limits to productivity in PA.…”

The mismeasure of conservation

“…The Durrell Wildlife Conservation Trust and the International Union for Conservation of Nature (IUCN)'s Species Survival Commission have estimated impacts with counterfactual measures of extinction risks of threatened species [92,93], and a notable recent impact-related initiative is IUCN'S Green List of Species [50]. The Rainforest Alliance and the Royal Society for the Protection of Birds have begun impact evaluations of their activities [82,94].…”

Assessing the global impact of targeted conservation actions on species abundance

“…When randomized experiments are not feasible, quasi-experimental designs, based on statistical methods such as matching, can be used instead (Stuart 2010;Joppa & Pfaff 2011;Butsic et al 2017;Geldmann et al 2019;Schleicher et al 2019). For example, annual population counts carried out within and outside protected areas can be matched on observable covariates, using the matched counts to determine how protection relates to population changes (Wauchope et al 2019a(Wauchope et al , 2020Jellesmark et al 2021).…”