Trophic rewilding presents regionally specific opportunities for mitigating climate change

Large-bodied mammalian herbivores can influence processes that exacerbate or mitigate climate change. Herbivore impacts are, in turn, influenced by predators that place top-down forcing on prey species within a given body size range. Here, we explore how the functional composition of terrestrial large herbivore and carnivore guilds vary between three mammal distribution scenarios: Present-Natural, Current-Day, and Extant-Native Trophic (ENT) Rewilding. Considering the effects of herbivore species weakly influenced by top-down forcing, we quantify the relative influence keystone large herbivore guilds have on methane emissions, woody vegetation expansion, fire dynamics, large-seed dispersal, and nitrogen and phosphorous transport potential. We find strong regional differences in the number of herbivores under weak top-down regulation between our three scenarios with important implications for how they will influence climate change relevant processes. Under the Present-Natural non-ruminant, megaherbivore, browsers were a particularly important guild across much of the world. Megaherbivore extinction and range contraction and the arrival of livestock means large, ruminant, grazers have become more dominant. ENT Rewilding can restore the Afrotropics and Indo-Malay to the Present-Natural benchmark, but causes top-down forcing of the largest herbivores to become common place elsewhere. ENT Rewilding will reduce methane emissions, but does not maximise Natural Climate Solution potential

The role of rewilding in mitigating hydrological extremes: State of the evidence

Landscape rewilding has the potential to help mitigate hydrological extremes by allowing natural processes to function. Our systematic review assessed the evidence base for rewilding-driven mitigation of high and low flows. The review uncovers a lack of research directly addressing rewilding, but highlights research in analogue contexts which can, with caution, indicate the nature of change. There is a lack of before-after studies that enable deeper examination of temporal trajectories and legacy effects, and a lack of research on the scrub and shrubland habitats common in rewilding projects. Over twice as much evidence is available for high flows compared to low flows, and fewer than one third of studies address high and low flows simultaneously, limiting our understanding of co-benefits and contrasting effects. Flow magnitude variables are better represented within the literature than flow timing variables, and there is greater emphasis on modeling for high flows, and on direct measurement for low flows. Most high flow studies report a mitigating effect, but with variability in the magnitude of effect, and some exceptions. The nature of change for low flows is more complex and suggests a higher potential for increased low flow risks associated with certain trajectories but is based on a very narrow evidence base. We recommend that future research aims to: capture effects on both high and low flow extremes for a given type of change; analyze both magnitude and timing characteristics of flow extremes; and examine temporal trajectories (before and after data) ideally using a full before-after-control-impact design. This article is categorized under: Human Water > Value of Water Science of Water > Hydrological Processes Science of Water > Water Extremes Water and Life > Conservation, Management, and Awareness

Functional traits of the world’s late Quaternary large-bodied avian and mammalian herbivores

Prehistoric and recent extinctions of large-bodied terrestrial herbivores had significant and lasting impacts on Earth’s ecosystems due to the loss of their distinct trait combinations. The world’s surviving large-bodied avian and mammalian herbivores remain among the most threatened taxa. As such, a greater understanding of the ecological impacts of large herbivore losses is increasingly important. However, comprehensive and ecologically-relevant trait datasets for extinct and extant herbivores are lacking. Here, we present HerbiTraits, a comprehensive functional trait dataset for all late Quaternary terrestrial avian and mammalian herbivores ≥10 kg (545 species). HerbiTraits includes key traits that influence how herbivores interact with ecosystems, namely body mass, diet, fermentation type, habitat use, and limb morphology. Trait data were compiled from 557 sources and comprise the best available knowledge on late Quaternary large-bodied herbivores. HerbiTraits provides a tool for the analysis of herbivore functional diversity both past and present and its effects on Earth’s ecosystems

Historical biogeography of the leopard (Panthera pardus) and its extinct Eurasian populations

Background: Resolving the historical biogeography of the leopard (Panthera pardus) is a complex issue, because patterns inferred from fossils and from molecular data lack congruence. Fossil evidence supports an African origin, and suggests that leopards were already present in Eurasia during the Early Pleistocene. Analysis of DNA sequences however, suggests a more recent, Middle Pleistocene shared ancestry of Asian and African leopards. These contrasting patterns led researchers to propose a two-stage hypothesis of leopard dispersal out of Africa: an initial Early Pleistocene colonisation of Asia and a subsequent replacement by a second colonisation wave during the Middle Pleistocene. The status of Late Pleistocene European leopards within this scenario is unclear: were these populations remnants of the first dispersal, or do the last surviving European leopards share more recent ancestry with their African counterparts? Results: In this study, we generate and analyse mitogenome sequences from historical samples that span the entire modern leopard distribution, as well as from Late Pleistocene remains. We find a deep bifurcation between African and Eurasian mitochondrial lineages (~ 710 Ka), with the European ancient samples as sister to all Asian lineages (~ 483 Ka). The modern and historical mainland Asian lineages share a relatively recent common ancestor (~ 122 Ka), and we find one Javan sample nested within these. Conclusions: The phylogenetic placement of the ancient European leopard as sister group to Asian leopards suggests that these populations originate from the same out-of-Africa dispersal which founded the Asian lineages. The coalescence time found for the mitochondrial lineages aligns well with the earliest undisputed fossils in Eurasia, and thus encourages a re-evaluation of the identification of the much older putative leopard fossils from the region. The relatively recent ancestry of all mainland Asian leopard lineages suggests that these populations underwent a severe population bottleneck during the Pleistocene. Finally, although only based on a single sample, the unexpected phylogenetic placement of the Javan leopard could be interpreted as evidence for exchange of mitochondrial lineages between Java and mainland Asia, calling for further investigation into the evolutionary history of this subspecies

Conservation and the problem with 'natural' - does rewilding hold the answer?

"Rewilding is the mass restoration of ecosystems and natural processes, accompanied or driven by the reintroduction of missing species." (George Monbiot, quoted in Sandom et al., forthcoming). This article considers the solution of 'rewilding': restoring species and ecosystems and allowing them to function within landscapes containing well-connected large core areas, often in a matrix of human land uses; not to recreate a particular past environment, rather to restore a lost natural process. </p

Conservation and the problem with 'natural' - does rewilding hold the answer?

"Rewilding is the mass restoration of ecosystems and natural processes, accompanied or driven by the reintroduction of missing species." (George Monbiot, quoted in Sandom et al., forthcoming). This article considers the solution of 'rewilding': restoring species and ecosystems and allowing them to function within landscapes containing well-connected large core areas, often in a matrix of human land uses; not to recreate a particular past environment, rather to restore a lost natural process. </p

Correction to Supporting Information for Lundgren et al., Introduced herbivores restore Late Pleistocene ecological functions.

© 2020 National Academy of Sciences. All rights reserved. The authors note that Dataset S1 was published without complete presence/absence information per species. In addition, references 72, 73, 77, 85, 98, 100, 101, 103, 109, 112, 117, 119, 121, 122, 126, 129, 131, and 324 were inadvertently omitted from the SI Appendix references list. The SI Appendix and Dataset S1 have been corrected online

Short-term response and recovery of bluebells (Hyacinthoides non-scripta) after rooting by wild boar (Sus scrofa)

Species reintroduction programmes should include consideration of potential impacts on key species in the recipient community. Wild boar (Sus scrofa) have been reintroduced into Britain after a 700-year absence. There is an urgent need to understand how this ecosystem engineer will affect plant communities in the habitats that it invades. We investigated the impact of rooting by wild boar on bluebells (Hyacinthoides non-scripta), a species that is highly valued for its impressive floral displays and is an important and legally protected component of the UK forest flora. We monitored bluebell performance over three growing seasons in woodland habitats that are routinely rooted by boar in southern England. H. non-scripta cover and reproductive performance were monitored in small-scale experimental exclosures to exclude boar, compared to open control plots, set up on areas that either had or had not been previously rooted. Immediate effects were that rooting significantly reduced the percentage cover and density of H. non-scripta plants, by up to 95 and 60 %, respectively, and also adversely affected the number of flowering stems. However, there was evidence that cessation of rooting brought about by excluding the boar enabled substantial recovery in percentage cover and the density of flowering stems within 2 years. A positive effect of rooting on germination may have assisted this recovery. Thus, the impact of wild boar rooting on bluebell populations is locally severe, but there is potential for rapid recovery if plants are protected. Long-term effects of sustained or frequently repeated rooting still need to be investigated

The role of large wild animals in climate change mitigation and adaptation

Two major environmental challenges of our time are responding to climate change and reversing biodiversity decline. Interventions that simultaneously tackle both challenges are highly desirable. To date, most studies aiming to find synergistic interventions for these two challenges have focused on protecting or restoring vegetation and soils but overlooked how conservation or restoration of large wild animals might influence the climate mitigation and adaptation potential of ecosystems. However, interactions between large animal conservation and climate change goals may not always be positive. Here, we review wildlife conservation and climate change mitigation in terrestrial and marine ecosystems. We elucidate general principles about the biome types where, and mechanisms by which, positive synergies and negative trade-offs between wildlife conservation and climate change mitigation are likely. We find that large animals have the greatest potential to facilitate climate change mitigation at a global scale via three mechanisms: changes in fire regime, especially in previously low-flammability biomes with a new or intensifying fire regime, such as mesic grasslands or warm temperate woodlands; changes in terrestrial albedo, particularly where there is potential to shift from closed canopy to open canopy systems at higher latitudes; and increases in vegetation and soil carbon stocks, especially through a shift towards below-ground carbon pools in temperate, tropical and sub-tropical grassland ecosystems. Large animals also contribute to ecosystem adaptation to climate change by promoting complexity of trophic webs, increasing habitat heterogeneity, enhancing plant dispersal, increasing resistance to abrupt ecosystem change and through microclimate modification