Biology subjects

Monsarrat, S.

Publications and source records attributed to Monsarrat, S..

5 recordsLinked to original sources

bioRxiv2023

Megafauna diversity and functional declines in Europe from the Last Interglacial (LIG) to the present

Aim: to estimate European megafauna diversity and functional declines in the present compared to the nearest in time modern-analogue climate period prior to the worldwide diffusion of Homo sapiens. Location: Europe. Time period: Last Interglacial (LIG; ca. 127,000 years ago) to present. Major taxa studied: wild, large ([≥]10 kg) terrestrial mammals. Methods: we assessed the distribution of 48 European megafauna species during the LIG using hindcasting modelling and fossil records. Then, we estimated the decline in megafauna community diversity and potential trait-based functional effects from the LIG to the present, accounting for climate differences between the two periods. Results: from the LIG to the present, species richness and community biomass across Europe dropped by 74.3% ({+/-} 9.9% SD) and 96.7% ({+/-} 4.1% SD), respectively. Functional diversity dropped by 59.1% ({+/-} 11.8% SD) for herbivores and by 48.2% ({+/-} 25.0% SD) for carnivores, while trait-informed potential vegetation and meat consumptions dropped by 91.1% ({+/-} 7.4% SD) and 61.2% ({+/-} 17.2% SD), respectively. The loss in megafauna diversity and associated ecological processes were high everywhere, but particularly in western Europe for carnivores and in the East European Plain for herbivores. We found that potential megafauna richness and functional patterns in the two periods were near identical if only climate-driven differences were considered. Main conclusions: severe, size-biased defaunation has degraded megafauna assemblages and megafauna-mediated ecological processes across Europe from the LIG to the present. These patterns cannot be explained by climate differences between the two periods, thus were likely driven by the impact of prehistoric Homo sapiens. The results suggest that the structure of wild ecosystems of the present strongly deviates from the evolutionary norm, notably with decreased functional heterogeneity and decreased fluxes of biogeochemical compounds across the trophic networks, highlighting the importance of ambitious policies of megafauna community restoration to support ecosystems functioning.

ecology↗

bioRxiv2022

Worldwide late-Quaternary population declines in extant megafauna are due to Homo sapiens rather than climate

The worldwide loss of large animal species over the past 100,000 years is evident from the fossil record, with climate and human impact as the most likely causes of megafauna extinctions. To help distinguish between these two scenarios, we analysed whole-genome sequence data of 142 species to infer their population size histories during the Quaternary. We modelled differences in population dynamics among species using ecological factors, paleoclimate and human presence as covariates. We report a significant population decline towards the present time in more than 90% of species, with larger megafauna experiencing the strongest decline. We find that population decline became ubiquitous approximately 100,000 years ago, with the majority of species experiencing their lowest population sizes during this period. We assessed the relative impact of climate fluctuations and human presence on megafauna dynamics and found that climate has limited explanatory power for late-Quaternary shifts in megafauna population sizes, which are largely explained by Homo sapiens arrival times. As a consequence of megafauna decline, total biomass and metabolic input provided by these species has drastically reduced to less than 25% compared to 100,000 years ago. These observations imply that the worldwide expansion of H. sapiens caused a major restructuring of ecosystems at global scale.

evolutionary biology↗

bioRxiv2021

Using recent baselines as benchmarks for megafauna restoration places an unfair burden on the Global South

The potential for megafauna restoration is unevenly distributed across the world, along with the socio-political capacity of countries to support these restoration initiatives. We show that choosing a recent baseline to identify species indigenous range puts a higher burden for megafauna restoration on countries in the Global South, which also have less capacity to support these restoration initiatives. We introduce the Megafauna Index, which considers large mammals potential species richness and range area at country-level, to explore how the responsibility for megafauna restoration distributes across the world according to four scenarios using various temporal benchmarks to define species indigenous range - current, historical (1500AD), mid-Holocene and Pleistocene. We test how the distribution of restoration burden across the world correlates to indicators of conservation funding, human development, and governance. Using a recent or historical baseline as a benchmark for restoration puts a higher pressure on African and southeast Asian countries while lifting the responsibility from the Global North, where extinctions happened a long time ago. When using a mid-Holocene or Pleistocene baseline, new opportunities arise for megafauna restoration in Europe and North America respectively, where countries have a higher financial and societal capacity to support megafauna restoration. These results contribute to the debate around benchmarks in rewilding initiatives and the ethical implications of using recent baselines to guide restoration efforts. We suggest that countries from the Global North should reflect on their responsibility in supporting global restoration efforts, by increasing their support for capacity building in the South and taking responsibility for restoring lost biodiversity at home.

ecology↗

bioRxiv2019

Anthropocene refugia: integrating history and predictive modelling to assess the space available for biodiversity in a human-dominated world

1.During periods of strong environmental change, some areas may serve as refugia, where components of biodiversity can find protection, persist and potentially expand from should conditions again become favourable. The refugia concept has previously been used in the context of climatic change, to describe climatically stable areas in which taxa survived past Quaternary glacial-interglacial oscillations, or where they might persist in the future under anthropogenic climate change. However, with the recognition that Earth has entered the Anthropocene, an era in which human activities are the dominant driving force on ecosystems, it is critical to also consider human pressures on the environment as factors limiting species distributions. Here, we present a novel concept, Anthropocene refugia, to refer to areas that provide spatial and temporal protection from human activities and that will remain suitable for a given taxonomic unit in the long-term. It integrates a deep-time perspective on species biogeography that provides information on the natural rather than current-day relictual distribution of species, with spatial information on modern and future anthropogenic threats. We define the concept and propose a methodology to effectively identify and map realised and potential current and future refugia, using examples for two megafauna species as a proof of concept. We argue that identifying Anthropocene refugia will improve biodiversity conservation and restoration by allowing better prediction of key areas for conservation and potential for re-expansions today and in the future. More generally, it forms a new conceptual framework to assess and manage the impact of anthropogenic activities on past, current and future patterns of species distributions.

ecology↗

bioRxiv2019

Shifted distribution baselines: neglecting long-term biodiversity records risks overlooking potentially suitable habitat for conservation management

Setting appropriate conservation measures to halt the loss of biodiversity requires a good understanding of species habitat requirements and potential distribution. Recent (past few decades) ecological data are typically used to estimate and understand species ecological niche. However, historical local extinctions may have truncated species-environment relationships, resulting in a biased perception of species habitat preferences. This may result in incorrect assessments of the area potentially available for their conservation. Incorporating long-term (centuries-old) occurrence records with recent records may provide better information on species-environment relationships and improve the modeling and understanding of habitat suitability. We test whether neglecting long-term occurrence records leads to an underestimation of species historical niche and potential distribution and identify which species are more vulnerable to this effect. We compare outputs of species distribution models and niche hypervolumes built using recent records only with those built using both recent and long-term (post-1500) records, for a set of 34 large mammal species in South Africa. We find that, while using recent records only is adequate for some species, adding historical records in the analyses impacts estimates of the niche and habitat suitability for fourteen species (41%) in our dataset, and that this effect is significantly higher for carnivores. These results show that neglecting long-term biodiversity records in spatial analyses risks misunderstanding, and generally underestimating, species niche, which in turn may lead to ill-informed management decisions, with significant implications for the effectiveness of conservation efforts.

ecology↗