Biology subjects

McRae, L.

Publications and source records attributed to McRae, L..

9 recordsLinked to original sources

bioRxiv2025

Navigating methodological decisions: Balancing rigor and data volume of the Canadian Living Planet Index

The Living Planet Index -- a biodiversity indicator that assesses the relative change of aggregate vertebrate abundance data -- is an indicator used in global and national biodiversity monitoring frameworks. In Canada, the LPI has been modified (C-LPI) -- adopting differing methodological choices relative to the global LPI. However, there is no clear consensus on the most appropriate analytical methods, particularly as they pertain to the treatment of zeros, confidence intervals and uncertainty, time series length and number of data points required, modelling of short time series, removal of outliers, weighting species, and the impact of baseline year selection. Our analysis transparently explores multiple methodological options and the consequent C-LPI output for each of these decision points. Our research does not evaluate the superiority of a single approach but rather provides transparency and accountability in C-LPI reporting. We hope that this will further strengthen the utility of the C-LPI and provide decision makers with the necessary information to appropriately interpret patterns, evaluate progress towards biodiversity targets, and inform conservation action.

ecology↗

bioRxiv2025

Halting predicted vertebrate declines requires tackling multiple drivers of biodiversity loss

Anthropogenic threats are reshaping Earths biodiversity at an unprecedented rate and scale1-3. Conservation policies often prioritise threats like habitat loss and exploitation based on their global prevalence. However, these assessments rarely quantify the impacts of individual or interacting threats, potential masking the true effects of the Anthropocene4-6. Here, we quantitatively analyse the trends of 3,129 vertebrate populations worldwide with documented exposure to specific and multiple threats. Populations impacted solely by habitat loss or exploitation, the most prevalent threats, do not show the fastest declines. Rather, populations exposed to disease, invasive species, pollution, and climate change decline more rapidly. However, habitat loss and exploitation - along with climate change - do act as additive interactive threats, amplifying population declines. Notably, these interactive threats contribute to population declines, more than temporal or spatial sources of variation. Finally, counterfactual scenarios show that to achieve global non-negative vertebrate population trends, we need to mitigate the effects of multiple threats. These findings underscore the urgency of addressing the compounding effects of multiple threats to halt biodiversity loss and suggest that the local-scale impacts of climate change may be more severe than previously recognized.

ecology↗

bioRxiv2023

How much data do we need? Reliability and data deficiency in global vertebrate biodiversity trends

Global biodiversity is facing a crisis, which must be solved through effective policies and on-the-ground conservation. But governments, NGOs, and scientists need reliable indicators to guide research, conservation actions, and policy decisions. Developing reliable indicators is challenging because the data underlying those tools is incomplete and biased. For example, the Living Planet Index tracks the changing status of global vertebrate biodiversity, but taxonomic, geographic and temporal gaps and biases are present in the aggregated data used to calculate trends. But without a basis for real-world comparison, there is no way to directly assess an indicators accuracy or reliability. Instead, a modelling approach can be used. We developed a model of trend reliability, using simulated datasets as stand-ins for the "real world", degraded samples as stand-ins for indicator datasets (e.g. the Living Planet Database), and a distance measure to quantify reliability by comparing sampled to unsampled trends. The model revealed that the proportion of species represented in the database is not always indicative of trend reliability. Important factors are the number and length of time series, as well as their mean growth rates and variance in their growth rates, both within and between time series. We found that many trends in the Living Planet Index need more data to be considered reliable, particularly trends across the global south. In general, bird trends are the most reliable, while reptile and amphibian trends are most in need of additional data. We simulated three different solutions for reducing data deficiency, and found that collating existing data (where available) is the most efficient way to improve trend reliability, and that revisiting previously-studied populations is a quick and efficient way to improve trend reliability until new long-term studies can be completed and made available.

ecology↗

bioRxiv2022

Recovering birds and mammals across Europe continue to be negatively impacted by threats but benefit from conservation measures

Even during ongoing global biodiversity losses and extinctions, numerous species have shown recoveries in terms of increased abundance and/or range extent. Understanding the mechanisms that contribute to, or limit, these recoveries is critical not just to ensure they continue, but to promote similar recoveries across broader ecosystems. Here, we explore the changes in abundance and range extent of selected 47 recovering species (24 mammals and 23 birds) in Europe using official data reported by EU Member States and supplemented using the Living Planet Index database. We investigate how the diversity of ongoing threats and conservation measures contribute to the likelihood and extent of recoveries. For birds, long-term recoveries were less likely among species impacted by a greater diversity of threats, although this may be mitigated by the diversity of conservation measures in place. Similarly, for mammals, populations with reported threats recovered less quickly while those with management actions in place recovered more quickly. To achieve the aims of the UN Decade on Restoration, we need to ensure, even for recovering species, that threats continue to be reduced and that conservation management actions are ongoing and effective.

ecology↗

bioRxiv2022

Past, present, and future of the Living Planet Index

As we enter the next phase of international policy commitments to halt biodiversity loss (e.g. Post-2020 Biodiversity Framework), biodiversity indicators will play an important role forming the robust basis upon which targeted, and time sensitive conservation actions are developed. Population trend indicators are perhaps the most powerful tool in biodiversity monitoring due to their responsiveness to changes over short timescales and their ability to aggregate species trends from global down to at a sub-national or even local scale. We consider how the project behind the foremost population level indicator - the Living Planet Index - has evolved over the last 25 years, its value to the field of biodiversity monitoring, and how its components have portrayed a compelling account of the changing status of global biodiversity through its application at policy, research and practice levels. We explore ways the project can develop to enhance our understanding of the state of biodiversity and share lessons learned to inform indicator development and mobilise action. O_TEXTBOXBox 1. The Living Planet Index Project The Living Planet Index project (the index, methodology, and database) and its secondary outputs (methods papers and R code, database and website, global index, and subset indices) have had wide-ranging applications within the fields of biodiversity monitoring and research, as well as across policy, education, and outreach. The Living Planet Index (LPI) is a biodiversity indicator which tracks trends in the relative abundance of wild vertebrate populations (where population is defined as to a single species in a defined location rather than the biological definition). Relative abundance captures how populations are changing over time on average in comparison to a reference point, or "baseline" (the LPI uses 1970). It is often described as analogous to a stock market index for species. The index is comprised of thousands of population time-series for vertebrate species from locations around the world; the trends from these populations are averaged to produce terrestrial, freshwater, and marine indices, which are further aggregated to a global LPI. The latest global LPI shows a decline of 68% between 1970 and 2016 globally 1. This is an average trend based on time-series data from 20,811 populations of 4,392 species of mammals, birds, reptiles, amphibians, and fish. The LPI database (LPD) can include population data for any species for which time-series population data could be found, regardless of threat status, or whether they show increasing or declining trends. These population time-series are sourced from scientific papers, online databases, government, and expert led published reports. They can be searched and downloaded from the project website (www.livingplanetindex.org). More technical information is available on the LPI stats website (http://stats.livingplanetindex.org/). C_TEXTBOX

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bioRxiv2022

Body mass and latitude as global predictors of vertebrate populations exposure to multiple threats

The interactive effects of multiple threats are one of the main causes of biodiversity loss, yet our understanding of what predisposes species to be impacted by multiple threats remains limited. Here we analyse a global dataset of over 7000 marine, freshwater, and terrestrial vertebrate populations, alongside trait, threat and geographical data, to identify the factors influencing the number of threats a species is subjected to at the population level. Out of a suite of predictors tested, we find that body mass and latitude both are broadly available for vertebrate species, and influence the number of threats a population is subjected to. Larger bodied species and those nearer the equator are typically affected by a higher number of threats. However, whilst this pattern broadly holds across ecosystems for most taxa, amphibians and reptiles show opposing trends. We suggest that latitude and body mass should be considered as key predictors to identify which vertebrate populations are likely to be impacted by multiple threats. These general predictors can help to better understand the impacts of the Anthropocene on global vertebrate biodiversity and design effective conservation policies.

ecology↗

bioRxiv2022

Assessing the global impact of targeted conservation actions on species abundance

In recent years, vertebrate population abundance has declined at unprecedented rates (WWF 2020). In response, targeted conservation measures - such as breeding programs or species-specific habitat management - have been applied to halt population declines, aid population recovery, and reduce and reverse the loss of biodiversity (Salafsky et al. 2008; Bolam et al. 2020). Until now, assessments of conservation actions have focused on the extent to which they reduce extinction risk, impact populations within protected areas, or increase the global area of land under protection (Hoffmann et al. 2010, 2015; Barnes et al. 2016; Maxwell et al. 2020; Bolam et al. 2020; Grace et al. 2021a). Here, we record and analyze conservation actions for 26,904 vertebrate populations from 4,629 species, to measure the impact of targeted conservation on vertebrate abundance. Using a counterfactual approach to represent population trends in the absence of conservation, we demonstrate that targeted actions have delivered substantial positive effects on the abundance of recipient vertebrate populations worldwide. We show that, in the absence of conservation, a global indicator of vertebrate abundance would have declined even more. Positive population trends were associated with vertebrate populations subject to species or habitat management. We demonstrate that targeted conservation actions can help to reverse global biodiversity loss and show the value of counterfactual analysis for impact evaluation - an important step towards reversing biodiversity declines.

ecology↗

bioRxiv2020

Body mass and latitude predict the presence of multiple stressors in global vertebrate populations

Multiple stressors are recognised as a key threat to biodiversity, but our understanding of what might predispose species to multiple stressors remains limited. Here we analyse a global dataset of over 7000 marine, freshwater, and terrestrial vertebrate populations, alongside species-specific trait data, to identify factors which influence the number of stressors a species is subjected to at the population level. We find that body mass and latitude can both influence the number of stressors a population is subjected to across ecosystems, with large-bodied species tending to be more threatened, except terrestrial amphibians which show the opposite trend. Latitudinal forecasts predict higher stressor numbers between 20{degrees}N and 40{degrees}N, and towards the poles. Global stressor distributions suggest a link between human population centres and stressor frequency generally impacting larger-bodied species. Latitude and body mass hence provide key predictive tools to identify which vertebrate populations are likely to be highly threatened, despite the strength of these trends differing between ecological system and taxonomic class.

ecology↗

bioRxiv2020

A global indicator of utilised wildlife populations: regional trends and the impact of management

The sustainable use of wildlife is a core aspiration of biodiversity conservation but is the subject of intense debate in the scientific literature as to how, and whether, species are best used and managed. While both positive and negative outcomes of sustainable use are known for specific taxa or local case studies, a global and regional picture of trends in wildlife populations in use is lacking. We use a global data set of over 11,000 time-series to derive indices of utilised and not utilised wildlife populations and assess global and regional changes, principally for mammals, birds and fishes. We also assess whether management makes a measurable difference to wildlife population trends, especially for the utilised species populations. Our results show that wildlife population trends globally are negative, but with utilised populations tending to decline more rapidly, especially in Africa and the Americas. Crucially, where utilised populations are managed, using a variety of mechanisms, there is a positive impact on the trend. It is therefore true that use of species can both be a driver of negative population trends, or a driver of species recovery, with numerous species and population specific case examples making up these broader trends. This work is relevant to the evidence base for the IPBES Sustainable Use Assessment, and to the development of indicators of sustainable use of species under the post-2020 Global Biodiversity Framework being developed under the Convention on Biological Diversity.

ecology↗