David Dudgeon

The University of Hong Kong | HKU

Aquatic insects comprise 64% of freshwater animal diversity and are widely used as bioindicators to assess water quality impairment and freshwater ecosystem health, as well as to test ecological hypotheses. Despite their importance, a comprehensive, global database of aquatic insect occurrences for mapping freshwater biodiversity in macroecological...

Non-native fishes are widespread in Hong Kong and many are likely to be established. Extensive field surveys, literature reviews, and citizen science data were used to determine the diversity, geographic distribution, potential introduction sources, and known impacts of non-native freshwater fishes in Hong Kong. In total, 95 species, including five...

Motivation: Aquatic insects comprise 64% of freshwater animal diversity and are

Habitat anthropization is a major driver of global biodiversity decline. Although most species are negatively affected, some benefit from anthropogenic habitat modifications by showing intriguing life-history responses. For instance, increased recruitment through higher allocation to reproduction or improved performance during early-life stages cou...

A herd of 15 Chinese elephants attracted international attention during their 2021 northward trek, motivating the government to propose establishment of an Asian elephant national park. However, planning is hampered by a lack of genetic information on the remaining populations in China. We collected DNA from 497 dung samples from all five populatio...

Conservation interventions for threatened species must be based on accurate assessments of the effects of anthropogenic pressures on habitat suitability. We used multiscale multivariable species-distribution modeling to evaluate habitat suitability for an Asian elephant (Elephas maximus) population in Shangyong Reserve, Yunnan Province, southwester...

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global...

The cover image is based on the Viewpoint A global agenda for advancing freshwater biodiversity research by Alain Maasri et al., https://doi.org/10.1111/ele.13931. Image Credit: Solvin Zankl. image

Sex-related differences in mortality are widespread in the animal kingdom. Although studies have shown that sex determination systems might drive lifespan evolution, sex chromosome influences on aging rates have not been investigated so far, likely due to an apparent lack of demographic data from clades including both XY (with heterogametic males)...

While a variety of anthropogenic impacts on lotic biodiversity have been documented, food-web responses to catchment development are poorly understood. We selected 27 stream food webs of comparable quality and conducted an analysis to assess the effect of catchment development on food-web structure. We quantified population densities, built-up area...

• Active and abandoned paddy fields are valuable habitats for aquatic fauna in monsoonal Asia. Changes in land use and farming practices have caused substantial losses of paddy-derived marshes in recent decades. Few of those remaining have been designated as protected areas for biodiversity or are managed for conservation. • Between 2014 and 2017,...

Fisheries resources in Hong Kong have been overexploited since the 1970s due to intensive bottom trawling and other fishing activities that have depleted stocks and destroyed marine habitat. To rehabilitate depleted fisheries resources, a permanent ban on trawling in Hong Kong territorial waters came into force on December 31, 2012. In order to det...

• Freshwater biodiversity is declining at an unprecedented rate. Freshwater conservationists and environmental managers have enough evidence to demonstrate that action must not be delayed but have insufficient evidence to identify those actions that will be most effective in reversing the current trend. • Here, the focus is on identifying essential...

• Exotic poeciliids have been reported to reduce abundance and richness of native fishes and, more generally, constrain the trophic niches of native counterparts. However, understanding of the consequences of poeciliids on native fishes in tropical streams is limited. • We conducted a survey of lowland streams in Hong Kong during 2018–19 to documen...

The wildlife trade is a major cause of species loss and a pathway for disease transmission. Socioeconomic drivers of the wildlife trade are influential at the local scale yet rarely accounted for in multinational agreements aimed at curtailing international trade in threatened species. In recent decades (1998-2018), approximately 421,000,000 threat...

Freshwater biodiversity is declining dramatically, and the current biodiversity crisis requires defining bold goals and mobilizing substantial resources to meet the challenges. While the reasons are varied, both research and conservation of freshwater biodiversity lag far behind efforts in the terrestrial and marine realms. We identify fifteen pres...

Biological invasion is globally pervasive and an increasing threat to biodiversity. We need to be able to predict the ecological impacts of alien species, in order to prioritize management of those expected to be most damaging. Comparisons of functional response (FR) between invaders and trophically similar natives has been proposed as useful for p...

Identification of the effect of anthropogenic threats on ecosystem is crucial. We used molecular tools and remote sensing to evaluate the population status of an isolated Asian elephant population in southwestern China in response to changes in habitat suitability between 1989 and 2019. A total of 22 unique genotypes were identified from 117 dung s...

Freshwater biodiversity is declining dramatically, and the current biodiversity crisis requires defining bold goals and mobilizing substantial resources to meet the challenges. While the reasons are varied, both research and conservation of freshwater biodiversity lag far behind efforts in the terrestrial and marine realms. We identify fifteen pres...

Bottom trawling, which is highly detrimental to seabed habitats, has been banned in some jurisdictions to mitigate the problems of habitat destruction and overfishing. However, most reports of ecosystem responses to trawling impacts originate from temperate latitudes, focusing on commercial species, and recovery of invertebrate macrobenthos from tr...

• The mosquitofish (Gambusia affinis: Poeciliidae) is one of the world's most widespread invaders, but our ability to predict the consequences for native species in the tropics is limited by a paucity of research and a lack of knowledge of how environmental factors influence mosquitofish impacts. • We undertook a field experiment using cages to man...

Cloeon micki sp. n., a new species of baetid mayfly from China is described and illustrated based on larval and imaginal stages associated by laboratory rearing. The new species is characterised by the presence of a dark brown or dark purple elliptical marking on abdominal tergites II and V, which readily distinguishes it from other members of the...

Nature has the potential to provide wide-ranging economic contributions to society – from ecosystem services to providing income to communities via fair trade of resources. Unsustainable trade in wildlife, however, threatens biodiversity and its ability to support communities and a functioning planet. It is therefore important to have clear systems...

Invasive poeciliid fishes have been negatively affecting recipient ecosystems globally. However, the ecological consequences of their invasions can vary seasonally and spatially, and according to species, limiting our ability to predict their effects. It is also unclear how their impacts differ from those of native fishes. We compared the effects o...

Trawl bans are relatively uncommon, particularly at the level of an entire coastal jurisdiction, and have seldom been studied in the tropics. A permanent territory-wide trawl ban has been implemented in Hong Kong coastal waters since the beginning of 2013. We used isotope-based metrics, in addition to traditional community measurements, to determin...

• Semi‐natural marshland is becoming increasingly prevalent in Asia as a result of the continuing abandonment of rice cultivation. Although these marshes are important habitats for aquatic animals, they are susceptible to terrestrialization. Large mammalian herbivores that can retard terrestrialization are in decline globally, but domesticated bovi...

The effects of climatic warming on tropical streams have received little attention, and field studies of such changes are generally lacking. Drifting insects from a Hong Kong forest stream were sampled for 36 months between 2013 and 2016, and compared with samples collected by identical methods in 1983‐84. Mean air temperatures rose by ~0.5°C (0.17...

While high efficiency and cost‐effectiveness are two merits of environmental DNA (eDNA) techniques for detecting aquatic organisms, the difficulty of designing species‐specific primers can result in significant expenditure of time and money. During the in silico stage of primer development, primer specificity is predicted with alignment techniques...

Cambridge Core - Ecology and Conservation - Freshwater Biodiversity - by David Dudgeon

Headwater streams are the first expression of a flowing-water ecosystem (between a spring and a small stream), and in many regions likely have intermittent or ephemeral flows. These ecosystems have very high edge to area ratios, and therefore are extremely sensitive to land-use effects, at reach and catchment (watershed) scales. The downstream limi...

Appropriation of fresh water to meet human needs is growing, and competition among users will intensify in a warmer and more crowded world. This essay explains why freshwater ecosystems are global hotspots of biological richness, despite a panoply of interacting threats that jeopardize biodiversity. The combined effects of these threats will soon b...

[This corrects the article DOI: 10.1371/journal.pone.0210552.].

Background and goal The study is conducted to facilitate conservation of migratory wader species along the East Asian-Australasian Flyway, particularly to 1) Identify hotspots of wader species richness along the flyway and effectively map how these might change between breeding, non-breeding and migratory phases; 2) Determine if the existing networ...

Movement of great knot (Calidris tenuirostris) over an annual migration cycle. Top: Non-breeding period—Oct, Nov, Dec, Jan, Feb, March; Bottom left: Northward migration—April, May; Bottom middle: Breeding period—June, July; Bottom right: southward migration—August, September. (TIF)

Total Area by species as estimated Birdlife Range maps and by MaxEnt modelled output, and the difference using Birdlife range maps to subtract MaxEnt outputs (unit: km2). (DOCX)

List of environmental variables considered and sources, or methodologies. (DOCX)

List of migration species and corresponding phases. (DOCX)

Part of the distribution of Limosa lapponica (Bar-tailed Godwit) as estimated by MaxEnt output and BirdLife range map. (TIF)

Global patterns of biodiversity have emerged for soil microorganisms, plants and animals, and the extraordinary significance of microbial functions in ecosystems is also well established. Virtually unknown, however, are large-scale patterns of microbial diversity in freshwaters, although these aquatic ecosystems are hotspots of biodiversity and bio...

In the 12 years since Dudgeon et al. (2006) reviewed major pressures on freshwater ecosystems, the biodiversity crisis in the world's lakes, reservoirs, rivers, streams and wetlands has deepened. While lakes, reservoirs and rivers cover only 2.3% of the Earth's surface, these ecosystems host at least 9.5% of the Earth's described animal species. Fu...

Degradation of freshwater ecosystems and the services they provide is a primary cause of increasing water insecurity, raising the need for integrated solutions to freshwater management. While methods for characterizing the multi-faceted challenges of managing freshwater ecosystems abound, they tend to emphasize either social or ecological dimension...

Plant litter represents a major basal resource in streams, where its decomposition is partly regulated by litter traits. Litter-trait variation may determine the latitudinal gradient in decomposition in streams, which is mainly microbial in the tropics and detritivore-mediated at high latitudes. However, this hypothesis remains untested, as we lack...

Forest loss has been associated with reduced survival in many vertebrates, and previous research on amphibians has mostly focused on effects at early life stages. Paramesotriton hongkongensis is a tropical newt that breeds in streams but spends up to 10 months per year in terrestrial habitats. Populations are threatened by habitat degradation and c...

The IUCN Red List is the most extensive source of conservation status assessments for species worldwide, but important gaps in coverage remain. Here we demonstrate the use of a spatial prioritization approach to efficiently prioritize species assessments to achieve increased and up-to-date coverage efficiently. We focus on freshwater fishes, which...

This chapter aims to assist biodiversity observation networks across the world in coordinating comprehensive freshwater biodiversity observations at national, regional or continental scales. We highlight special considerations for freshwater biodiversity and methods and tools available for monitoring. We also discuss options for storing, accessing,...

Accumulating impacts Anthropogenic climate change is now in full swing, our global average temperature already having increased by 1°C from preindustrial levels. Many studies have documented individual impacts of the changing climate that are particular to species or regions, but individual impacts are accumulating and being amplified more broadly....

Translocation of ‘nuisance’ snakes is frequently employed on a large scale in densely populated areas in order to mitigate human-wildlife conflict. However, the methods used are often applied haphazardly and are rarely evaluated, especially in tropical Asia. The objective of this study was to assess the effects of long-distance translocation on the...

Biological invasions have had severe impacts on ecosystems globally, particularly affecting freshwater habitats. In the aquatic realm, marine environments have received less attention from researchers than their freshwater counterparts, and comparisons of the relative susceptibility of coastal and inland waters to alien species and their consequent...

Both hydropower dams and global warming pose threats to freshwater fish diversity. While the extent of global warming may be reduced by a shift towards energy generation by large dams in order to reduce fossil-fuel use, such dams profoundly modify riverine habitats. Furthermore, the threats posed by dams and global warming will interact: for exampl...

Fish distribution data. (CSV)

GAM analysis for different RCPs under global warming versus three biodiversity indices in 2050 and 2070. The blue line indicates the spline curve. (TIF)

Example of MAXENT results. Graphical maps show the habitat suitability for shovel-jaw carp, Onychostoma gerlachi (Cyprinidae), under projections derived from different scenarios. Scenario names in parentheses correspond to those in S2 Table. Solid lines in the maps show the distribution threshold (habitat suitability: 0.05) of O. gerlachi. (TIF)

An example of synergistic effects. Compared to the dam-construction scenario, the distributional range of mudcarp, Cirrhinus jullieni (Cyprinidae), was projected to expand under the synergistic effects of dams and global warming. However, because of drainage-basin fragmentation caused by dams, the full expansion of distribution that would have occu...

GAM analysis for total generating capacity versus three biodiversity indices. The blue line indicates the spline curve. (TIF)

Differences in response patterns to dams and global warming. Most fish species showed a contraction in range extent under the planned-dam scenarios (assuming 100% of planned dams were built), while global-warming scenario ip85bi70 had little effect on average habitable area, although the extent of variation was sensitive to species identity. A simi...

Species list used in the analysis. (PDF)

Scenario names and details. (PDF)

The Hong Kong newt (Paramesotriton hongkongensis) is a tropical stream-dwelling salamandrid native to Hong Kong and coastal areas of Guangdong Province, China, inhabiting small rocky hill streams and surrounding forests. It is categorized as "near threatened" on the IUCN Red List because of range-wide habitat degradation and vulnerability to over-e...

Plant litter breakdown is a key ecological process in terrestrial and freshwater ecosystems. Streams and rivers, in particular, contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter breakdown in fresh waters, particularly at large scales. We presen...

The lower, potamonic parts of the Ganges–Brahmaputra, the Ayeyarwady (Irrawaddy), the Salween, the Chao Phraya and the Mekong and Lancang Rivers are among the longest and most productive rivers for inland fisheries in the world. Except for the Chao Phraya, they arise on the Tibetan Plateau. All have steep and turbulent upper courses within deep mou...

Seasonal changes in emergence rates of aquatic insects and the relative abundance of volant aquatic and terrestrial insects were monitored using emergence, UV-light and Malaise traps over a 14-month period along two forested streams in Hong Kong. Although the mean annual emergence rates in terms of aquatic insect numbers, ranged from 9399 to 17,127...

The dietary dependence on volant aquatic insects of eight species of predatory arthropods from three different orders was determined by stable isotope analyses in combination with three-source, two-isotope (C and N) Bayesian mixing models. The predators were collected from riparian zones along three streams in tropical Hong Kong during both the wet...

Top-down control of benthic communities by fishes in temperate and Neotropical streams has received considerable attention, yet relatively little is known about the occurrence or strength of such top-down control in tropical Asian streams. We undertook pool-scale removals of an entire macroconsumer assemblage of fishes and predatory shrimp, as well...