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Assessing how time lags influence the response of mammal and bird populations to change

Assessing how time lags influence the response of mammal and bird populations to change
Complex, delayed impacts of environmental change on mammal and bird abundance trends. (a) Predicted population trends in response to combinations of scaled environmental change. While warming and land conversion (upper right of each panel) are generally associated with strong population declines, small mammals might benefit from such conditions. (b) Projected indices of relative abundance, based on modeled populations and alternative socio-economic scenarios, highlight important consequences of ecological lags. First, population trends up to 2050, both increases and declines, may already be largely "locked-in" (gray shading) due to their dependence on environmental change that has already occurred. Second, lags of 30 years or more mean that current environmental change will substantially affect abundance trends in 2050 and beyond. In (a), colored lines correspond to IUCN Red List threat categories based on population declines of 30% (yellow; Vulnerable), 50% (orange; Endangered) or 80% (red; Critically endangered) over 10 years (A2 criteria). In (b), the horizontal line is set at 1, the baseline for our projections. Shaded areas show future projections that are fully (dark) or partially (light) dependant on environmental change prior to 2010 (in all but medium mammals, CC is associated with longer lags and thus the lighter shading). The y-axes in each panel of (b) are kept constant to emphasize the variability between projections for different size classes. Credit: Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.0464

A team of zoologists and life scientists from the Zoological Society of London, the Natural History Museum in London and Our World in Data at the Global Change Data Lab has conducted an assessment of how time lags influence the response of mammal and bird populations to both climate and land-use change. In their study, reported in Proceedings of the Royal Society B, the group analyzed data from the Living Planet Database and used it to manipulate models to assess the true impact of change on mammal and bird populations.

A large number of animals are at risk of extinction due to human activities. The researchers in this new effort suggest that there are currently two main drivers that put mammals and birds at risk: loss of habitat and . They also note that models that are currently used to assess animal population risks do not include time lag influences, which, they contend, lead to serious miscalculations. In their work, time lags are defined as periods of time that it takes for a given population of creatures to start declining due to external factors, such as loss of land or reductions in available food.

Prior to diving into the data, the team set themselves the goal of answering five general questions: Do lag times better explain changes in population than other factors? Are lags better described in years or generations? Are there differences in lags between species? Do vary across lags? And what are the ecological repercussions of lags on future population trends?

In analyzing entries in the database, which stores information on more than 600 species of mammals and birds, the team narrowed their focus to 751 populations, including 712 species in 664 locations. They found that lag times varied widely from less than 10 years to more than 40, depending on the species. They note that the longer lag times for some species suggests that many of them may already be at risk.

The team then used the results of their analysis to reconfigure and found that inclusion of lag times shows that many more species of mammals and birds are at risk than has been shown in other studies. They suggest that unless changes are made soon, targets adopted by governments to protect certain species might already be out of reach.

More information: Richard Cornford et al, Ongoing over-exploitation and delayed responses to environmental change highlight the urgency for action to promote vertebrate recoveries by 2030, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.0464

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Citation: Assessing how time lags influence the response of mammal and bird populations to change (2023, April 20) retrieved 29 September 2023 from https://phys.org/news/2023-04-lags-response-mammal-bird-populations.html
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