The increasing abandonment of marginal land creates new opportunities for restoration, reintroduction, and rewilding, but what do these terms mean in a rapidly and irreversibly changing world? The ...‘re’ prefix means ‘back’, but it is becoming clear that the traditional use of past ecosystems as targets and criteria for success must be replaced by an orientation towards an uncertain future. Current opinions in restoration and reintroduction biology range from a defense of traditional definitions, with some modifications, to acceptance of more radical responses, including assisted migration, taxon substitution, de-extinction, and genetic modification. Rewilding attempts to minimize sustained intervention, but this hands-off approach is also threatened by rapid environmental change.
Abandonment of agricultural land provides an opportunity for creating new ecosystems, but the traditional use of past ecosystems as targets is likely to be inappropriate in a time of rapid environmental change.
There is no agreement among conservationists about how to replace the historically based reference frame, with opinions ranging from minor modification to the acceptance of increasingly radical alternatives including moving species outside their current native ranges, using non-native taxon substitutions to maintain key functions, and the acceptance of novel ecosystems that are different from any past analogs.
New technologies will facilitate the genetic modification of threatened species and make the ‘de-extinction’ of at least some species possible, providing new, controversial options for conservationists.
Future debates seem likely to increasingly focus on the degree of human intervention that is desirable as ‘wildness’ is seen as an increasingly important attribute. Rewilding attempts to minimize sustained intervention, but this approach is also threatened by rapid environmental change.
•The term ‘Anthropocene’ was coined in 2000 to refer to the current, human-dominated time period.•It is being considered as a potential geological epoch, following the Holocene.•Ecologists have used ...it to argue for more attention to human-dominated ecosystems.•In conservation biology, it has sparked a divisive debate on the philosophy and aims of the discipline.
The term ‘Anthropocene’ was first used in the year 2000 to refer to the current time period in which human impacts are at least as important as natural processes. It is currently being considered as a potential geological epoch, following on from the Holocene. While most environmental scientists accept that many key environmental parameters are now outside their Holocene ranges, there is no agreement on when the Anthropocene started, with plausible dates ranging from the Late Pleistocene megafaunal extinctions to the recent globalization of industrial impacts. In ecology, the Anthropocene concept has focused attention on human-dominated habitats and novel ecosystems, while in conservation biology it has sparked a divisive debate on the continued relevance of the traditional biocentric aims.
Tropical forests exchange more carbon dioxide (CO2) with the atmosphere than any other vegetation type and, thus, form a crucial component of the global carbon cycle. However, the impacts of ...anthropogenic climate change on drought occurrence and intensity could weaken the tropical forest carbon sink, with resulting feedback to future climates. We urgently need a better understanding of the mechanisms and processes involved to predict future responses of tropical forest carbon sequestration to climate change. Recent progress has been made in the study of drought responses at the molecular, cellular, organ, individual, species, community, and landscape levels. Although understanding of the mechanisms is incomplete, the models used to predict drought impacts could be significantly improved by incorporating existing knowledge.
Forecasts from climate models suggest an increased risk of droughts in tropical forests over the next few decades, potentially threatening the large existing carbon sink.
Natural droughts and rainfall exclusion experiments result in decreased tree growth and increased mortality, with large trees most affected in both cases.
Mechanisms at the tree level are still incompletely understood. Hydraulic failure seems to be robustly associated with tree death, but other failure modes, including carbon starvation and phloem failure, may also be significant.
The drought tolerance of economic trees has been increased by experiment transfers of genes from model plants, suggesting that at least some components of the molecular mechanisms are universal. Some elements of drought responses at the cellular and molecular level have been identified in model plants, but we are still a long way from a full mechanistic understanding.
Drought responses at the community level and above include changes in species composition and, where humans are present, interactions between droughts, forest fragmentation, and fire.
Conserving biodiversity in the face of ever-increasing human pressure is hampered by our lack of basic information on species occurrence, distribution, abundance, habitat requirements, and threats. ...Obtaining this information requires efficient and sensitive methods capable of detecting and quantifying true occurrence and diversity, including rare, cryptic and elusive species. Environmental DNA (eDNA) is an emerging technique that can increase our ability to detect and quantify biodiversity, by overcoming some of the challenges of labor-intensive traditional surveys. The application of eDNA in ecology and conservation has grown enormously in recent years, but without a concurrent growth in appreciation of its strengths and limitations. In many situations, eDNA may either not work, or it may work but not provide the information needed. Problems with (1) imperfect detection, (2) abundance quantification, (3) taxonomic assignment, (4) eDNA spatial and temporal dynamics, (5) data analysis and interpretation, and (6) assessing ecological status have all been significant. The technique has often been used without a careful evaluation of the technical challenges and complexities involved, and a determination made that eDNA is the appropriate method for the species or environment of interest. It is therefore important to evaluate the scope and relevance of eDNA-based studies, and to identify critical considerations that need to be taken into account before using the approach. We review and synthesize eDNA studies published to date to highlight the opportunities and limitations of utilizing eDNA in ecology and conservation. We identify potential ways of reducing limitations in eDNA analysis, and demonstrate how eDNA and traditional surveys can complement each other.
Before the end of this century, tropical rainforests will be subject to climatic conditions that have not existed anywhere on Earth for millions of years. These forests are the most species-rich ...ecosystems in the world and play a crucial role in regulating carbon and water feedbacks in the global climate system; therefore, it is important that the probable impacts of anthropogenic climate change are understood. However, the recent literature shows a striking range of views on the vulnerability of tropical rainforests, from least to most concern among major ecosystems. This review, which focuses on the impact of rising temperatures, examines the evidence for and against high vulnerability, identifies key research needs for resolving current differences and suggests ways of mitigating or adapting to potential impacts.
Conservation biology needs a bigger toolbox to meet unprecedented challenges. Genomics, fueled by declining sequencing costs, offers novel tools with increased precision for genetic questions ...previously answered with a few molecular markers, as well as completely new possibilities. Metabarcoding promises quicker, cheaper, and more accurate assessments of biodiversity in groups that are difficult to assess by traditional methods, while sequencing low-quality DNA extends the range of useable materials to include museum specimens, archeological remains, and environmental samples. Genomic and transcriptomic data can be used to assess the potential of populations to adapt to new challenges. In the near future, gene-editing tools may help endangered species cope with change, while gene drives control unwanted species and help wanted ones. De-extinction has become a serious prospect.
The conservation of plants has not generated the sense of urgency—or the funding—that drives the conservation of animals, although plants are far more important for us. There are an estimated 500,000 ...species of land plants (angiosperms, gymnosperms, ferns, lycophytes, and bryophytes), with diversity strongly concentrated in the humid tropics. Many species are still unknown to science. Perhaps a third of all land plants are at risk of extinction, including many that are undescribed, or are described but otherwise data deficient. There have been few known global extinctions so far, but many additional species have not been recorded recently and may be extinct. Although only a minority of plant species have a specific human use, many more play important roles in natural ecosystems and the services they provide, and rare species are more likely to have unusual traits that could be useful in the future. The major threats to plant diversity include habitat loss, fragmentation, and degradation, overexploitation, invasive species, pollution, and anthropogenic climate change. Conservation of plant diversity is a massive task if viewed globally, but the combination of a well-designed and well-managed protected area system and ex situ gap-filling and back-up should work anywhere. The most urgent needs are for the completion of the global botanical inventory and an assessment of the conservation status of the 94% of plant species not yet evaluated, so that both in and ex situ conservation can be targeted efficiently. Globally, the biggest conservation gap is in the hyperdiverse lowland tropics and this is where attention needs to be focused.
Despite the importance of plant diversity to human wellbeing, and the threats to its survival, plant conservation receives far less support compared with vertebrate conservation.Plants can be ...conserved in situ, in protected areas, and ex situ, in living collections, seed banks, or cryogenic storage. At least one option is available for all species that need it, but no single method works for all.Achieving zero plant extinction requires completion of the plant inventory, status assessment for all known species, digitization of all herbarium specimens with links to other resources in an online global metaherbarium, and separate recovery plans for each threatened species.The major bottleneck is the shortage of skilled people. New technologies, machine learning, and citizen scientists can extend the reach of experts, but training and incentives are needed to increase their number.
Despite the importance of plants for humans and the threats to their future, plant conservation receives far less support compared with vertebrate conservation. Plants are much cheaper and easier to conserve than are animals, but, although there are no technical reasons why any plant species should become extinct, inadequate funding and the shortage of skilled people has created barriers to their conservation. These barriers include the incomplete inventory, the low proportion of species with conservation status assessments, partial online data accessibility, varied data quality, and insufficient investment in both in and ex situ conservation. Machine learning, citizen science (CS), and new technologies could mitigate these problems, but we need to set national and global targets of zero plant extinction to attract greater support.
Seed dispersal is a key process in plant communities and frugivory is very important in vertebrate communities. This paper updates a review of frugivory and seed dispersal by vertebrates in the ...Oriental Region (tropical and subtropical Asia) published in 1998. The major conclusions remain the same. Small fruits are consumed by a wide range of potential seed dispersal agents, including species that thrive in small forest fragments and degraded landscapes. Larger and larger-seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation, and habitat loss. Controlling hunting in both forest areas and the agricultural matrix must be a top priority for conservation. A lot more natural history information has been added to the literature since 1998. This reinforces previous evidence for the importance of hornbills, bulbuls, elephants, gibbons, civets, and fruit bats in seed dispersal, and suggests that the roles of green pigeons, macaques, rodents, bears, and deer were previously underestimated. The taxa for which additional natural history observations would be most valuable include fish, pheasants, pigeons, babblers, rodents, and even-toed ungulates. For other animal taxa, future frugivory and seed dispersal studies need to focus more on the fitness consequences for both the plants and the animals.
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