Defaunation, the loss or population decline of medium and large native vertebrates represents a significant threat to the biodiversity of tropical ecosystems. Here we review the anthropogenic drivers ...of defaunation, provide a brief historical account of the development of this field, and analyze the types of biological consequences of this impact on the structure and functioning of tropical ecosystems. We identify how defaunation, operating at a variety of scales, from the plot to the global level, affects biological systems along a gradient of processes ranging from plant physiology (vegetative and reproductive performance) and animal behavior (movement, foraging and dietary patterns) in the immediate term; to plant population and community dynamics and structure leading to disruptions of ecosystem functioning (and thus degrading environmental services) in the short to medium term; to evolutionary changes (phenotypic changes and population genetic structure) in the long-term. We present such a synthesis as a preamble to a series of papers that provide a compilation of our current understanding of the impact and consequences of tropical defaunation. We close by identifying some of the most urgent needs and perspectives that warrant further study to improve our understanding of this field, as we confront the challenges of living in a defaunated world.
Animals and the zoogeochemistry of the carbon cycle Schmitz, Oswald J; Wilmers, Christopher C; Leroux, Shawn J ...
Science (American Association for the Advancement of Science),
12/2018, Letnik:
362, Številka:
6419
Journal Article
Recenzirano
Predicting and managing the global carbon cycle requires scientific understanding of ecosystem processes that control carbon uptake and storage. It is generally assumed that carbon cycling is ...sufficiently characterized in terms of uptake and exchange between ecosystem plant and soil pools and the atmosphere. We show that animals also play an important role by mediating carbon exchange between ecosystems and the atmosphere, at times turning ecosystem carbon sources into sinks, or vice versa. Animals also move across landscapes, creating a dynamism that shapes landscape-scale variation in carbon exchange and storage. Predicting and measuring carbon cycling under such dynamism is an important scientific challenge. We explain how to link analyses of spatial ecosystem functioning, animal movement, and remote sensing of animal habitats with carbon dynamics across landscapes.
Anthropocene defaunation, the global extinction of faunal species and populations and the decline in abundance of individuals within populations, has been predominantly documented in terrestrial ...ecosystems, but indicators suggest defaunation has been more severe in freshwater ecosystems. Marine defaunation is in a more incipient stage, yet pronounced effects are already apparent and its rapid acceleration seems likely. Defaunation now impacts the planet's wildlife with profound cascading consequences, ranging from local to global coextinctions of interacting species to the loss of ecological services critical for humanity. Slowing defaunation will require aggressively reducing animal overexploitation and habitat destruction; mitigating climate disruption; and stabilizing the impacts of human population growth and uneven resource consumption. Given its omnipresence, defaunation should receive status of major global environmental change and should be addressed with the same urgency as deforestation, pollution, and climatic change. Global action is needed to prevent defaunation's current trajectory from catalyzing the planet's sixth major extinction.
Biodiversity is essential to human well-being, but people have been reducing biodiversity throughout human history. Loss of species and degradation of ecosystems are likely to further accelerate in ...the coming years. Our understanding of this crisis is now clear, and world leaders have pledged to avert it. Nonetheless, global goals to reduce the rate of biodiversity loss have mostly not been achieved. However, many examples of conservation success show that losses can be halted and even reversed. Building on these lessons to turn the tide of biodiversity loss will require bold and innovative action to transform historical relationships between human populations and nature.
Defaunation in the Anthropocene Dirzo, Rodolfo; Young, Hillary S.; Galetti, Mauro ...
Science (American Association for the Advancement of Science),
07/2014, Letnik:
345, Številka:
6195
Journal Article
Recenzirano
Odprti dostop
We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on ...animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this "Anthropocene defaunation"; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet's sixth mass extinction and also a major driver of global ecological change.
Large herbivores and carnivores (the megafauna) have been in a state of decline and extinction since the Late Pleistocene, both on land and more recently in the oceans. Much has been written on the ...timing and causes of these declines, but only recently has scientific attention focused on the consequences of these declines for ecosystem function. Here, we review progress in our understanding of how megafauna affect ecosystem physical and trophic structure, species composition, biogeochemistry, and climate, drawing on special features of PNAS and Ecography that have been published as a result of an international workshop on this topic held in Oxford in 2014. Insights emerging from this work have consequences for our understanding of changes in biosphere function since the Late Pleistocene and of the functioning of contemporary ecosystems, as well as offering a rationale and framework for scientifically informed restoration of megafaunal function where possible and appropriate.
Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ...ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human–wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology.
Human activities have altered the abundance and distribution of animals, reshaping ecosystems into novel and generally more depauperate configurations. Whereas, overhunting and habitat loss threaten ...numerous species, predation release and subsidies from agriculture and food waste benefit others. Although these impacts combined can generate multiple different outcomes, we propose that, depending on the prevalence of different anthropogenic drivers, mammalian communities are pushed towards one of three main defaunation syndromes: Herbivore-dominated, seed predator-dominated or mesopredator-dominated systems. The extirpation of top predators favors herbivore-dominated assemblages, while habitat loss and overhunting eliminate large-bodied herbivores, resulting in the dominance of smaller-bodied seed predators and mesopredators. Within fragmented landscapes where top predators are absent, mesopredator-dominated systems emerge supported by food subsidies from the surrounding agricultural matrix. Based on a large dataset of camera-trap studies, we show that continuous Neotropical forests with top predators exhibit a greater balance between these guilds and landscape structure explain composition variation according to these syndromes. The prevalence of one guild over others has profound effects on ecological processes, threatening ecosystem services and human health and may be the dominant scenario in the Anthropocene.
Rewilding constitutes an ecological recovery approach that has been promoted to restore vanished ecological functions by replacing recently extinct or extirpated species through the reintroduction of ...the missing species or the introduction of their non-native functional analogues. In recent years we have witnessed many rewilding projects worldwide, with emphasis on (re)introducing large-bodied mammals (megafauna) in order to restore top-down trophic interactions and the associated trophic cascades and to promote self-regulating biodiverse ecosystems (i.e., trophic rewilding). However, this emphasis on large-sized mammals in conservation initiatives have ignored the importance of other taxa, such as reptiles, which can equally serve as potential candidates in rewilding projects. There appears to be a gap in the scientific literature in regard to the importance and effect of different taxa with the potential to play equal and important roles in ecosystem functionality and restoration. Consequently, there is a need for a comprehensive and systematic review of the subject. Here, we highlight the significance of rewilding using reptiles, focusing on herbivorous species, for the purpose of ecological restoration; and discuss how the taxonomic bias in rewilding initiatives has led to uneven conservation goals for certain vertebrate groups. Finally, we outline the consequences for reptilian rewilding under climate change and relate to how this group may fare in these conservation initiatives.
Dispersal is a critical ecological process that modulates gene flow and contributes to the maintenance of genetic and taxonomic diversity within ecosystems. Despite an increasing global understanding ...of the arbuscular mycorrhizal (AM) fungal diversity, distribution and prevalence in different biomes, we have largely ignored the main dispersal mechanisms of these organisms. To provide a geographical and scientific overview of the available data, we systematically searched for the direct evidence on the AM fungal dispersal agents (abiotic and biotic) and different propagule types (i.e. spores, extraradical hyphae or colonized root fragments). We show that the available data (37 articles) on AM fungal dispersal originates mostly from North America, from temperate ecosystems, from biotic dispersal agents (small mammals) and AM fungal spores as propagule type. Much lesser evidence exists from South American, Asian and African tropical systems and other dispersers such as large-bodied birds and mammals and non-spore propagule types. We did not find strong evidence that spore size varies across dispersal agents, but wind and large animals seem to be more efficient dispersers. However, the data is still too scarce to draw firm conclusions from this finding. We further discuss and propose critical research questions and potential approaches to advance the understanding of the ecology of AM fungi dispersal.
PDF
