Ecological science for ecosystem services and the stewardship of Natural Capital

1. National and international assessments are increasingly highlighting the unsustainable use of earth's natural resources in the face of population increase, growing material affluence and global change. In all likelihood, the use and degradation of natural resources will continue. 2. In contrast to resource depletion, the concept of natural capital emphasises how the environment is an asset to be managed, to ensure that the benefits which flow from it are sustained for future generations. These benefits are the ecosystem goods and services upon which all people rely for their continued survival and well-being both now and, ideally, in perpetuity. 3. Despite their importance, the evidence-base and quantitative understanding of links between biodiversity, ecosystem function and ecosystem services are insufficient to allow informed use and management. Moreover, the concepts of natural capital and ecosystem services are insufficiently mainstream to influence decisions that currently favour the production of food and fibre rather than less tangible services such as climate regulation, air and water purification, pollination or the contributions of environment to health. 4. There are specific challenges to ecological science in this interdisciplinary endeavour: specifically, to develop frameworks for identifying and monitoring natural capital; to parameterise factors affecting ecosystem services and their resilience to change; to integrate the complexity of ecological systems into ecosystem service valuation; and to characterise the synergies and trade-offs between ecosystem services in different management and policy scenarios. 5. Synthesis and applications. The five papers in this Special Profile exemplify just some of the leading work through which ecologists in the UK are contributing nationally and internationally to these needs, stemming from the UK National Ecosystem Assessment - the first national scale exercise of its type in the world. We expect a major, worldwide increase in work on ecosystem services and natural capital in future as decisions on ecosystem use of management are squeezed increasingly between the needs of exploitation and protection

Microplastic ingestion by riverine macroinvertebrates

Although microplastics are a recognised pollutant in marine environments, less attention has been directed towards freshwater ecosystems despite their greater proximity to possible plastic sources. Here, we quantify the presence of microplastic particles (MPs) in river organisms upstream and downstream of five UK Wastewater Treatment Works (WwTWs). MPs were identified in approximately 50% of macroinvertebrate samples collected (Baetidae, Heptageniidae and Hydropsychidae) at concentrations up to 0.14 MP mg tissue−1 and they occurred at all sites. MP abundance was associated with macroinvertebrate biomass and taxonomic family, but MPs occurred independently of feeding guild and biological traits such as habitat affinity and ecological niche. There was no increase in plastic ingestion downstream of WwTW discharges averaged across sites, but MP abundance in macroinvertebrates marginally increased where effluent discharges contributed more to total runoff and declined with increasing river discharge. The ubiquity of microplastics within macroinvertebrates in this case study reveals a potential risk from MPs entering riverine food webs through at least two pathways, involving detritivory and filter-feeding, and we recommend closer attention to freshwater ecosystems in future research

Estimating the size distribution of plastics ingested by animals

The ingestion of plastics appears to be widespread throughout the animal kingdom with risks to individuals, ecosystems and human health. Despite growing information on the location, abundance and size distribution of plastics in the environment, it cannot be assumed that any given animal will ingest all sizes of plastic encountered. Here, we use published data to develop an allometric relationship between plastic consumption and animal size to estimate the size distribution of plastics feasibly ingested by animals. Based on more than 2000 gut content analyses from animals ranging over three orders of magnitude in size (lengths 9 mm to 10 m), body length alone accounts for 42% of the variance in the length of plastic an animal may ingest and indicates a size ratio of roughly 20:1 between animal body length and the largest plastic the animal may ingest. We expect this work to improve global assessments of plastic pollution risk by introducing a quantifiable link between animals and the plastics they can ingest

Birds as bioindicators of river pollution and beyond: specific and general lessons from an apex predator

Birds can be impacted by pollution but are seldom used as bioindicators. One exception involves the Dippers Cinclus spp., a genus of five passerines adapted uniquely to swim and dive in rivers on five continents to feed on aquatic invertebrates and small fishes. Here, we review the effectiveness of Dippers as pollution indicators while identifying further opportunities, caveats and uncertainties that are transferable to other indicator organisms. Dippers have been used as biodindicators i) through relationships linking their distribution, breeding performance and behaviour to river pollution through effects on prey quality and quantity; ii) where contaminants occur in their eggs, tissues, faeces or regurgitates, notably metals (Hg, Se), persistent pollutants (e.g. PCBs, PBDEs, DDE, HEOD) and microplastics. Most data are from C. cinclus in Europe and C. mexicanus in North America. While some pollution effects on Dipper distribution or fitness are well-evidenced, particularly acidification, the resulting impairments are not sufficient to diagnose the source of impact without additional data on water quality or prey abundance. Dippers in these cases provide a general rather than definitive indication of pollution. For contaminants, Dippers have revealed the distribution of specific pollutants at scales ranging from point-sources and regions to different continents. Influences of land use, trophic pathways, diet-shifts, contaminant transport, intergenerational transfer and trends through time have all been identified and supported by detailed knowledge of prey use, territoriality, dispersal, migration, life history, isotopic signatures and energetics. We suggest opportunities to expand the role of Dippers as bioindicators into other locations (Asia and South America), other influences on water quality (e.g. agriculture, wastewater), other contaminants (e.g. PFAs, pharmaceuticals) and through developments in modern biology such as ‘omics. Initial data also show that Dippers could integrate the effects on rivers of habitat modification, flow modification and climate change by indicating effects both directly and through interactions with other multiple stressors. This group of birds illustrates how fundamental ecological information aids the development of bioindicators but reveals the importance of using complementary environmental data when diagnosing bioindicator response. We suggest these are important lessons for ecological indicators more generally

Lifting the veil: richness measurements fail to detect systematic biodiversity change over three decades

While there is widespread recognition of human involvement in biodiversity loss globally, at smaller spatial extents, the effects are less clear. One reason is that local effects are obscured by the use of summary biodiversity variables, such as species richness, that provide only limited insight into complex biodiversity change. Here, we use 30 yr of invertebrate data from a metacommunity of 10 streams in Wales, UK, combined with regional surveys, to examine temporal changes in multiple biodiversity measures at local, metacommunity, and regional scales. There was no change in taxonomic or functional a-diversity and spatial b-diversity metrics at any scale over the 30-yr time series, suggesting a relative stasis in the system and no evidence for on-going homogenization. However, temporal changes in mean species composition were evident. Two independent approaches to estimate species niche breadth showed that compositional changes were associated with a systematic decline in mean community specialization. Estimates of species-specific local extinction and immigration probabilities suggested that this decline was linked to lower recolonization rates of specialists, rather than greater local extinction rates. Our results reveal the need for caution in implying stasis from patterns in a-diversity and spatial b-diversity measures that might mask non-random biodiversity changes over time. We also show how different but complementary approaches to estimate niche breadth and functional distinctness of species can reveal long-term trends in community homogenization likely to be important to conservation and ecosystem function

Evidence of biological recovery from gross pollution in English and Welsh rivers over three decades

Uncertainty around the changing ecological status of European rivers reflects an evolving array of anthropogenic stressors, including climate change. Although previous studies have revealed some recovery from historical pollution in the 1990s and early-2000s, there are contrasting trends among pollutants across Europe and recovery may have even stalled or been reversed. To provide more contemporary evidence on trends and status, here we investigate changes in English and Welsh river macroinvertebrate communities over almost 30 years (1991–2019) using a network of nearly 4000 survey locations. Analysis comprised: i) trends in taxonomic and functional richness, community composition and ecological traits, ii) gains, losses and turnover of taxa, and the overall homogeneity of macroinvertebrate communities nationally, and iii) an exploration of how temporal trends varied with catchment characteristics. Taxonomic richness increased, primarily in the 1990s, whilst a shift towards pollution-sensitive taxa continued throughout the study period, accompanied by a growing prevalence in traits such as preferences for fast-flowing conditions, coarser substrata, and ‘shredding’ or ‘scraping’ feeding strategies. Changes consistent with improvement occurred in both urbanised and agricultural catchments, but were more pronounced in urban rivers as they gained pollution sensitive taxa that were otherwise more prevalent in rural rivers. Overall, these results indicate continuing biological recovery from organic pollution, consistent with national scale trends in water quality. Results reemphasise the importance of looking at multiple facets of diversity, with periods of near-constant richness disguising changes in taxonomic and functional composition. Whilst this national-scale picture is broadly positive, we highlight the need to investigate more local variations or pollutants that depart from this aggregate picture

River organisms as indicators of the distribution and sources of persistent organic pollutants in contrasting catchments

Persistent organic pollutants (POPs) continue to threaten aquatic organisms, but risk assessments are restricted by poor knowledge of the distribution and quantity of these substances in different biota. Assessments on aquatic invertebrates are particularly scarce. Here, we investigate variation in polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorines (OCs) in sediments, biofilms, macroinvertebrates and fish across rivers in South Wales (UK). Persistent PCB (−118, −153, −180) and PBDE congeners (BDE-47, -99, −100), and OCs (p,p’-dichlorodiphenyldichloroethylene [p,p’-DDE] and dieldrin [HEOD]) dominated the POPs detected, indicating links to historical emissions. Low concentrations of less persistent PBDEs, PCBs and OCs, however, suggest more contemporary sources. Concentrations of POPs were 2–22 times greater in fish than invertebrates, but their detection frequency (>90%) and concentrations (0–304 ng g−1 wet weight) were higher in these organisms than in sediments or biofilms (<10%; 0–12 ng g−1 wet weight). Invertebrates and fish also contained several PCB congeners (28, 52, 77 and 105) and p,p’-dichlorodiphenyltrichloroethane (p,p’-DDT) that were not detected in the environmental samples. Concentrations of PBDEs, PCBs and OCs differed among invertebrate taxa and feeding guilds. After controlling for significant variation among sample types and taxa, PBDEs were found to increase with urban land cover, while increased PCBs were associated with urban land cover and wastewater discharge. These data illustrate how body burdens of POPs across invertebrate and fish taxa provide valuable information on the spatial variation and likely sources of persistent pollutants in freshwater ecosystems. More work is required to resolve differences in POP contamination between taxonomic groups

River birds as potential indicators of local- and catchment-scale influences on Himalayan river ecosystems

Rivers are affected by changes in catchment land-use and other modifications to their channel, floodplains and riparian zones. Such changes can affect biodiversity downstream, and specialist river birds might indicate the effects across multiple scales and through different ecological pathways. The risks of catchment-scale effects on rivers are especially acute in the Himalayan mountains, where the world’s greatest diversity of river birds occupies one of the most rapidly changing riverine environments on Earth. Here, we use multivariate analysis on data collected over two years to investigate the distribution of this group of birds in relation to natural and anthropogenic variations in riverine habitats along one of the major headwaters of the Ganges. River bird distribution was linked to channel character, bank morphology, aspects of river flow and land use. Riverine specialists were associated significantly with the least modified reaches characterised by faster flows, exposed bedrocks, banks with pebbles, boulders with more intact riverine forests. Our data provide evidence from which to develop specialist river birds as cost-effective indicators of human impacts on river ecosystems, but further work is needed to separate the effects of natural and anthropogenic influences. Such work could also guide conservation action to help balance the exploitation of catchment ecosystem services with the protection of river biodiversity

Testing the ecosystem service cascade framework for Atlantic salmon

Aligning nature protection with human well-being for the UN Sustainable Development Goals implies that conservation monitoring should indicate the sustainability of ecosystem services (ES). Here we test the value of the ES cascade framework using national, multi-decadal data for an iconic freshwater fish, the Atlantic salmon Salmo salar. For the first time, we assemble all long-term monitoring data for England and Wales along the ES cascade for this species from resource to benefit: juvenile density to measure the biological resource, returning adult numbers to measure potential ES use, and rod catches and angling effort as measures of actual ES use. We aimed to understand how the ES cascade framework reconciled conservation with ES sustainability targets. Only some linkages along the ES cascade could be evidenced: in catchments where juveniles declined, rod catches also generally decreased, but angling effort declined everywhere irrespective of the biological resource trends. We suggest that i) programmes focused on juvenile monitoring provide an early-warning system for ES provision as well as nature conservation, ii) the ES cascade framework can reconcile nature conservation and ES sustainability if monitoring efforts link biological resources fully to the ES, and ES monitoring explicitly relates biological resources to human use