Using change trajectories to study the impacts of multi-annual habitat loss on fledgling production in an old forest specialist bird

Abstract

The loss and subdivision of habitat into smaller and more spatially isolated units due to human actions has been shown to adversely affect species worldwide. We examined how changes in old forest cover during eight years were associated with the cumulative number of fledged offspring at the end of study period in Eurasian treecreepers (Certhia familiaris) in Central Finland. We were specifically interested in whether the initial level of old forest cover moderated this relation. We applied a flexible and powerful approach, latent growth curve modelling in a structural equation modeling (SEM) framework, to create trajectories describing changes in old forest cover through time, and studied how this change at both the territory core and landscape scales impacted fledging numbers. Our main finding was that at the territory core scale the negative impact of habitat loss on fledging numbers was lessened by the higher levels of initial forest cover, while no association was found at the landscape scale. Our study highlights a powerful, but currently under-utilised methodology among ecologists that can provide important information about biological responses to changes in the environment, providing a mechanistic way to study how land cover dynamics can affect species responses.

Synergistic effects of climate and land‐use change influence broad‐scale avian population declines

“…In addition, climate and land‐use changes are often correlated over space and time (Oliver & Morecroft, ), which poses an additional challenge to study design and inference. As a result, most studies have either assessed the impacts of only a single global change driver (Le Tortorec et al, ) to avoid correlation issues, or have fit static models examining the influence of multiple drivers and inferred synergistic changes by predicting into the future based on projections of climate and land‐use change (i.e., models are fit to data from a single point in time and projected into the future under the assumption that contemporary patterns will hold; Heubes et al, , Jetz, Wilcove, & Dobson, , Sohl, , Vermaat et al, ). Models assessing only a single driver risk incorrectly attributing impacts due to frequent confounding between climate and land cover (Oliver & Morecroft, ), whereas projections are necessarily speculative due to substantial uncertainty in future climate and land‐use patterns and the assumption that species responses will exhibit stationarity, despite evidence to the contrary (e.g., Gutiérrez Illán et al, , Yegorova, Betts, Hagar, & Puettmann, ).…”