Extinction in the Anthropocene.

Human activity has dramatically accelerated both species extinctions and introductions, and the balance of these two processes is generally expected to reduce biodiversity and increase taxonomic homogenization. However, few tests of this hypothesis have been made. We tested whether new macroinvertebrate invaders in North American freshwaters can replace the recent loss of biodiversity, particularly focusing on molluscs. We found that both crustaceans and molluscs are overrepresented among endangered and recently extinct species, as well as among invaders. For molluscs, the number of recently extinct species (79 species) was more than twice that for exotic species (38 species). In addition, molluscan invaders are from different taxonomic families than recently extinct or endangered species. While most extinct and endangered molluscs are from streams and rivers, invaders preferentially colonize lakes and reservoirs. The impact of humans on species introductions and extinctions increases with spatial scale (from local to continental scales), resulting in the increased phylogenetic dissimilarity between introduced species and native communities. Construction of dams and alteration of the flow regimes of lotic systems will continue to lead to the extinction of native species, and promote the spread of invaders, resulting in a loss of biodiversity and taxonomic homogenization.

Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna

We investigated lake sediments from Großer Ursee, Landkreis Ravensburg, Allgäu, Baden-Württemberg, to explore whether human activity was delayed and less intense at higher sites compared to those in the adjacent lower area around Bodensee (Lake Constance). A 11.1 m high resolution pollen profile from the centre of the lake was analysed, which covers the late Würm and complete Holocene sequence, providing a continuous pollen record of 1,092 samples. Human and climate induced vegetation and landscape change is discussed. The history of human impact indicated in this profile at around 700 m in the western Allgäu, with a precipitation above 1,000 mm/year and with a less favourable climate is compared with human impact in adjacent lower landscapes, with a more favourable climate for agriculture such as the Bodensee region. Since the Neolithic period, differences in vegetation development between the regions were mainly caused by a varying intensity of human impact which itself was strongly influenced by climatic differences. In the lowlands with a warm and dry climate, human impact started earlier and was stronger than in less favourable areas. Finally, the regular occurrence of Trapa natans at Großer Ursee, much more frequent there than in the adjacent warmer landscape to the west, is discussed in terms of various ecological factors.

Birds have long fascinated scientists and travellers, so their distribution and abundance through time have been better documented than those of other organisms. Many bird species are known to have gone extinct, but information on subspecies extinctions has never been synthesised comprehensively. We reviewed the timing, spatial patterns, trends and causes of avian extinctions on a global scale, identifying 279 ultrataxa (141 monotypic species and 138 subspecies of polytypic species) that have gone extinct since 1500. Species extinctions peaked in the early 20th century, then fell until the mid 20th century, and have subsequently accelerated. However, extinctions of ultrataxa peaked in the second half of the 20th century. This trend reflects a consistent decline in the rate of extinctions on islands since the beginning of the 20th century, but an acceleration in the extinction rate on continents. Most losses (78.7% of species and 63.0% of subspecies) occurred on oceanic islands. Geographic foci of extinctions include the Hawaiian Islands (36 taxa), mainland Australia and islands (29 taxa), the Mascarene Islands (27 taxa), New Zealand (22 taxa) and French Polynesia (19 taxa). The major proximate drivers of extinction for both species and subspecies are invasive alien species (58.2% and 50.7% of species and subspecies, respectively), hunting (52.4% and 18.8%) and agriculture, including non-timber crops and livestock farming (14.9% and 31.9%). In general, the distribution and drivers of subspecific extinctions are similar to those for species extinctions. However, our finding that, when subspecies are considered, the extinction rate has accelerated in recent decades is both novel and alarming.

This chapter presents results of a scenario-building exercise, designed to explore future trends in forest biodiversity in four forest areas, and the potential implications for policy development and implementation. An expert consultation conducted in a workshop environment identified 11 principal pressures responsible for biodiversity loss in Latin America, namely land-cover change, fire, invasive species, browsing animals, pollution, mining, development of infrastructure (roads, pipelines, dams), logging/fuelwood extraction, habitat fragmentation, climate change and loss of keystone species and ecological structures. The relative importance of these different pressures was assessed in each of four study areas, namely Central Veracruz (Mexico), the Highlands of Chiapas (Mexico), Rio Maule-Cobquecura (Region VII, Chile) and Los Muermos-Ancud (Region X, Chile). Scores were generated for each area describing both variation in intensity of the pressures over time and their potential impacts on different components of biodiversity. The scoring process was used to support development of three scenario narratives for each area, namely business as usual, deepening conservation crisis and effective conservation. Recommendations for policy development and implementation are presented for each study area, based on these scenarios. The results indicate that action on global commitments to reduce biodiversity loss must take account of the geographical variation in the relative importance of different pressures and their varying impacts on different biodiversity components. Policy developments and practical conservation action will need to be tailored for individual areas, defined at the sub-national level.

The Rejtek I. Rock Shelter in the Bükk Mountains of the inner Western Carpathian region plays an important role in the Late Pleistocene and Holocene environmental historical analyses. The investigations of the cave sediment accumulated from the end of the Pleistocene and the recovered paleontological finds, together with the archaeological artefacts, provided an opportunity to develop stratigraphic classifications. In addition, by comparing archaeostratigraphic, lithostratigraphic and biostratigraphic data, it was possible to link environmental and prehistoric events. The importance of the site is shown by both the mollusc and floral cold- and warm-tolerant species that were present in the area during the Late Pleistocene. The early expansion of thermophilous species indicates the presence of a refuge already during the Late Pleistocene. Based on the documents of the excavation, the previous works, the sediment sequence, as well as the sediment samples and the filling material of the mollusc shells, together with the new chronology, we were able to clarify the relative order of the excavated layers and the description of the sediment types in the Rejtek I. Rock Shelter.

Reducing the rate of species extinction and protecting biodiversity are major international concerns. The loss of biodiversity is closely related to international trade as an inevitable result of industrial agglomeration and improvements in green economy efficiency. In contrast to previous studies on biodiversity loss from the perspectives of deforestation, hunting, and fire, this study examines biodiversity loss from an international trade perspective, calculates the biodiversity footprint of each country as an indicator of biodiversity loss, and innovatively elaborates on the theoretical mechanisms of industrial agglomeration, green economy efficiency, and biodiversity loss. An empirical analysis used panel data from 148 countries from 2006 to 2020. This study identifies that industrial agglomeration directly and indirectly aggravates biodiversity loss through green economy efficiency, which mediates the relationship between industrial agglomeration and biodiversity loss. The effects of industrial agglomeration and green economy efficiency on biodiversity loss driven by export trade in developed and developing countries are consistent with the benchmark test results. The effect of industrial agglomeration on green economy efficiency is positive in developed countries and vice versa in developing countries. By region, green economy efficiency can significantly mitigate the embodied biodiversity loss in the export trade in Asia, Africa, and North America, whereas its influence in Europe and North America is insignificant. This study extends the perspective of biodiversity research from the natural to economic fields, delves into the underlying economic causes of the current state of trade-driven biodiversity loss, and provides important evidence for reducing biodiversity losses caused by international trade.

The Bering Land Bridge: a moisture barrier to the dispersal of steppe–tundra biota?

1. To address effects of land use and human overexploitation on wildlife populations, it is essential to better understand how human activities have changed species composition, diversity and functioning. Theoretical studies modelled how network properties change under human-induced, non-random species loss. However, we lack data on realistic species-loss sequences in threatened, real-world food webs to parameterize these models. 2. Here, we present a first size-structured topological food web of one of the most pristine terrestrial ecosystems in the world, the Serengeti ecosystem (Tanzania). The food web consists of 95 grouped nodes and includes both invertebrates and vertebrates ranging from body masses between 10(-7) and 10(4) kg. 3. We study the topological changes in this food web that result from the simulated IUCN-based species-loss sequence representing current species vulnerability to human disturbances in and around this savanna ecosystem. We then compare this realistic extinction scenario with other extinction sequences based on body size and connectance and perform an analysis of robustness of this savanna food web. 4. We demonstrate that real-world species loss in this case starts with the biggest (mega) herbivores and top predators, causing higher predator-prey mass ratios. However, unlike theoretically modelled linear species deletion sequences, this causes poor-connected species to be lost first, while more highly connected species become lost as human impact progresses. This food web shows high robustness to decreasing body size and increasing connectance deletion sequences compared with a high sensitivity to the decreasing connectance deletion scenario. 5. Furthermore, based on the current knowledge of the Serengeti ecosystem, we discuss how the focus on food web topology alone, disregarding nontrophic interactions, may lead to an underestimation of human impacts on wildlife communities, with the number of trophic links affected by a factor of two. 6. This study underlines the importance of integrative efforts between the development of food web theory and basic field work approaches in the quantification of the structure of interaction networks to sustain natural ecosystems in a changing world.

Cabrera’s vole, Microtus (Iberomys) cabrerae, is a currently endemic species restricted to Spain and Portugal. Its present day distribution is fragmentary, but in the past it was broadly distributed across the Iberian Peninsula, with the exception of the northern part of the Peninsula. Various hypotheses have been expounded to explain the retraction of the species since the beginning of the Holocene: 1) the climate changes produced in the Bronze Age; 2) the human impact on the restricted habitat of the species; and 3) its direct competition with other species with similar environmental requirements, such as the southern water vole (Arvicola sapidus), an Iberian endemism. In this paper, we discuss these hypotheses regarding the distribution of the species fossil record in the Late Pleistocene and beginning of the Holocene, as well as its current distribution. The most plausible hypothesis for its retraction is human impact, which has destroyed the habitat of the species with the development of agriculture and road infrastructures and the increasing human population

Habitat loss, fragmentation and degradation are drivers of major declines in biodiversity and species extinctions. The actual causes of species population declines following habitat change are more difficult to discern. In this thesis I attempt to identify, based on published data on mobility and their ecological responses to fragmentation, some of the processes that may have led to patterns of decline for 10 woodland-dependent birds in fragmented woodlands of central Victoria, Australia. Eight species had been identified as ‘decliners’ (species that disappear from suitable patches when landscape-level tree cover falls below species-specific thresholds) and two as ‘tolerant’ species (whose occurrence in suitable habitat patches is independent of landscape tree cover). I investigated the contribution of decreased structural connectivity on functional connectivity as a cause of the observed declines. A set of landscape connectivity models was constructed of each species covering a range of plausible values. The two dominant algorithms for summarising effective distances used in modelling complex fragmentation patterns in landscape genetics—least-cost path and circuit distance—were used to construct these models The results of the two methods were compared and circuit distance was determined to be the more appropriate approach for use in my study system. Choice of algorithm and null model were important influences on inferences in landscape genetics. I predicted (1) fragmentation would impede dispersal and gene flow of ‘decliners’ but not of ‘tolerant’ species; and that fragmentation effects would be stronger (2) in the least mobile species, (3) in the more philopatric sex and (4) in the more fragmented region. These predictions were then tested with a large empirical genetic dataset (2198 individuals from 63 sites across a 170 x 50-km study area). I fitted models specific to sex and geographic zone in order to account for sex-biased dispersal and potential scale- and configuration-specific effects. As expected, four of the least mobile decliners showed reduced genetic connectivity. Responses were sex specific in the two least mobile species. The tolerant species and (unexpectedly) four of the more mobile decliners showed no reduction in gene flow. Weaker genetic effects were observed in the geographic zone with more aggregated vegetation, consistent with gene flow being unimpeded by landscape structure. These results indicate that, excepting the most sedentary species in our system, the movement of the more dispersive sex maintains overall genetic connectivity across fragmented landscapes in the study area. I examined relationships among configuration, extent and status of native vegetation and three commonly used indicators of individual body condition and chronic stress in 13 species, two measures of changes to population processes (sex ratio and individual homozygosity) in 10 species and allelic richness in five species. Little support for relationships between site or landscape characteristics and individual or population response variables was found. These findings, along with related work to which I contributed, but that does not form part of the thesis, highlighted the need for management to increase both connectivity, for the least mobile species, and critical resource availability for other species to conserve these declining species.

Several studies provide evidence that social, economic, political, and conservation-related factors impact cross-national biodiversity loss. One theoretical argument concerning biodiversity loss that has not been directly assessed involves the relationship between species loss and neoliberalism. Generally, neoliberalism promotes free markets. This has become a dominant philosophy across nations (though the strength of neoliberalism varies cross-nationally) and affects how nations interact with one another as resource users and providers. Given how neoliberal policies work to integrate nations into a single global capitalist economy, we assess neoliberalism’s effects on threatened species alongside a nation’s position in the global world-system. The current study examines nine sets of negative binomial regression models analyzing the effect of neoliberalism, world-system position, and a set of control variables on species biodiversity loss across a sample of 104 countries for which all relevant data were available. We find some support that neoliberalism increases biodiversity loss in fully assessed species (birds and amphibians). We also find support for the hypothesis that there is more biodiversity loss in the periphery and semi-periphery of the world-system (compared with core countries) in fully assessed threatened species. We argue that the results support previous research showing the sociological drivers of biodiversity loss.

Late Quaternary megafaunal extinctions in India: How much do we know?

Studies of biodiversity loss commonly imply that species extinctions occurred as a direct result of initial human arrival and thus are attributable to stewardship failures of Indigenous Peoples. However, recent studies have suggested this assumption is not supported by the evidence, prompting a global reevaluation of existing assumptions. To assess the relationship between human arrival in the Hawaiian Islands and documented declines in waterbird biodiversity, we reviewed empirical evidence from paleoecological studies. We first identified the time period that extinct Hawaiian waterbird species were last observed within the fossil record. We then evaluated four hypotheses proposed to explain drivers of Holocene waterbird extinctions: (1) the overkill hypothesis; (2) the deforestation hypothesis; (3) the climate change hypothesis; and (4) the species introductions hypothesis. Of the 18 extinct waterbird species evaluated in this study, 10 were last observed in the fossil record prior to Polynesian arrival, 6 were last observed in the fossil record during the Polynesian era, and 2 were last visually observed after European arrival. Extinctions that possibly occurred during the Polynesian era were likely caused by a suite of factors, some anthropogenic and some non‐anthropogenic. Our findings contradict previous studies that attributed Holocene waterbird extinctions to hunting and deforestation by Native Hawaiians and suggest a future line of inquiry regarding a proposed “regime shift extinctions” hypothesis to explain complex impacts of human‐mediated and climatic drivers of extinction in the Anthropocene.

Global biodiversity is declining with substantial losses of populations, species and habitats causing a significant impact on human life. Holistic and integrated approach for biodiversity conservation requires concrete and urgent action. Although there is increasing concern over the loss of species and degradation of habitat, still more innovative efforts are required. Biobanking holds immense promise to provide biomaterial for conservation of fish germplasm. Establishment of repositories along with gene banks could provide opportunities for collaboration among the leading experts in the fields of fish ecology, physiology, and cryobiology to synthesize effective ways for conservation of fish genetic resources, and discuss what needs to be done to increase the impact in the next century. The article reviews different causes for loss of fish biodiversity, the ways to overcome the situation and advocates cell line repository as an alternative aid to conserve fish germplasm.