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The establishment probability of introduced alien fish can be context dependent, varying according to factors including propagule pressure and biotic resistance. The influence of nutrient enrichment on establishment outcomes of alien fishes is uncertain, yet this is a common anthropogenic stressor of many freshwaters. Here, the small-bodied alien topmouth gudgeon Pseudorasbora parva was used in mesocosms to experimentally test how a gradient of nutrient enrichment affected their growth rates, recruitment and trophic ecology. A ‘Control’ represented ambient, mesotrophic conditions, while treatments covered three levels of nutrient enrichment: low (eutrophic), medium (hypertrophic) and high (very hypertrophic). Each mesocosm was seeded with 6 mature P. parva (equal sex ratio) at the start of their reproductive season. After 100 days, length increments of the adult fish were significantly elevated in the low treatment, and these fish had also produced significantly higher numbers of 0+ fish compared to all other treatments. The trophic niche width of the mature fish was substantially higher in the control than the treatments, but this did not appear to confer any advantages to them in somatic growth rate or reproductive output. These results suggest that the nutrient status of receiving waters can have substantial impacts on the outcomes of fish introductions, where eutrophic conditions can assist the rapid population establishment of some alien species.

As a high-quality non-polluting energy source, coalbed methane is widely used in power generation, automobile fuel and other fields. Moreover, the concentration of coalbed methane can be effectively reduced by exploiting and utilizing coalbed methane so as to eliminate the gas accidents fundamentally. In the coal mining area, the exploiting of coalbed methane resources are closely related to the hydrogeological conditions. This paper discusses the controlling effect of hydrogeological conditions on coalbed methane exploitation mainly from chemical characteristics, the hydraulic connection between aquifers, groundwater recharge, runoff and discharge characteristics and so on. The results showed that the water-bearing zones were recharged by precipitation. The isotopic characteristics of the coalbed water, the taiyuan limestone aquifer, the ordovician limestone aquifer showed that the groundwater were ancient which are formed earlier and the coalbed water expressed a definite drift feature of D. There had a weak hydraulic interaction between different aquifers. Mg2+, Cl-, HCO3-, TDS are the monitoring index of drainage production water. If the hydrogeological problems are frequently occurred When mining, it is necessary to analyze the hydrogeological conditions objectively and study the relationship between them to make the coalbed methane scientifically exploitation to improve efficiency and quality of coalbed methane.

Invasive alien species are likely to interact with climate change, thus necessitating management that proactively addresses both global changes. However, invasive species managers’ concerns about the effects of climate change, the degree to which they incorporate climate change into their management, and what stops them from doing so remain unknown. Therefore, we surveyed natural resource managers addressing invasive species across the U.S. about their priorities, concerns, and management strategies in a changing climate. Of the 211 managers we surveyed, most were very concerned about the influence of climate change on invasive species management, but their organizations were significantly less so. Managers reported that lack of funding and personnel limited their ability to effectively manage invasive species, while lack of information limited their consideration of climate change in decision-making. Additionally, managers prioritized research that identifies range-shifting invasive species and native communities resilient to invasions and climate change. Managers also reported that this information would be most effectively communicated through conversations, research summaries, and meetings/symposia. Despite the need for more information, 65% of managers incorporate climate change into their invasive species management through strategic planning, preventative management, changing treatment and control, and increasing education and outreach. These results show the potential for incorporating climate change into management, but also highlight a clear and pressing need for more targeted research, accessible science communication, and two-way dialogue between researchers and managers focused on invasive species and climate change.

The relationship between body mass (M) and size class abundance (N) depicts patterns of community structure and energy flow through food webs. While the general assumption is that M and N scale linearly (on log–log axes), nonlinearity is regularly observed in natural systems, and is theorized to be driven by nonlinear scaling of trophic level (TL) with M resulting in the rapid transfer of energy to consumers in certain size classes. We tested this hypothesis with data from 31 stream food webs. We predicted that allochthonous subsidies higher in the web results in nonlinear M–TL relationships and systematic abundance peaks in macroinvertebrate and fish size classes (latter containing salmonids), that exploit terrestrial plant material and terrestrial invertebrates, respectively. Indeed, both M–N and M–TL significantly deviated from linear relationships and the observed curvature in M–TL scaling was inversely related to that observed in M–N relationships. Systemic peaks in M–N, and troughs in M–TL occurred in size classes dominated by generalist invertebrates, and brown trout. Our study reveals how allochthonous resources entering high in the web systematically shape community size structure and demonstrates the relevance of a generalized metabolic scaling model for understanding patterns of energy transfer in energetically ‘open’ food webs.

Multiple stressors, such as warming and invasions, often occur together and have nonadditive effects. Most studies to date assume that stressors operate in perfect synchrony, but this will rarely be the case in reality. Stressor sequence and overlap will have implications for ecological memory - the ability of past stressors to influence future responses. Moreover, stressors are usually defined in an anthropocentric context: what we consider a short-term stressor, such as a flood, will span multiple generations of microbes. We argue that to predict responses to multiple stressors from individuals to the whole ecosystem, it is necessary to consider metabolic rates, which determine the timescales at which individuals operate and therefore, ultimately, the ecological memory at different levels of ecological organization.

Body mass–abundance (M‐N) allometries provide a key measure of community structure, and deviations from scaling predictions could reveal how cross‐ecosystem subsidies alter food webs. For 31 streams across the UK, we tested the hypothesis that linear log‐log M‐N scaling is shallower than that predicted by allometric scaling theory when top predators have access to allochthonous prey. These streams all contained a common and widespread top predator (brown trout) that regularly feeds on terrestrial prey and, as hypothesised, deviations from predicted scaling increased with its dominance of the fish assemblage. Our study identifies a key beneficiary of cross‐ecosystem subsidies at the top of stream food webs and elucidates how these inputs can reshape the size‐structure of these ‘open’ systems.

In many ecological communities, the effects of exotic species are likely to extend beyond their direct interactions with natives, due to indirect effects. This dynamic might be particularly consequential in cases where invasive insects or other exotic herbivores target foundation plant species in the communities they invade. In this study at a site in western Massachusetts, we used experimental transplants to gauge the potential effects of a decline in the evergreen conifer Tsuga canadensis due to ongoing spread of two exotic insect pests on a liverwort, Bazzania trilobata, whose distribution is closely linked to dense stands of this conifer in the northeastern USA. After 4 years, transplanted B. trilobata samples moved to forest areas with lower abundance of T. canadensis declined significantly, particularly on sites with higher solar radiation, as determined by local slope and aspect. In addition, samples manually cleared of deciduous leaf litter were ∼ 17% larger than those exposed to natural accumulation of leaf litter, indicating a direct negative effect of deciduous trees on the liverwort that might increase as these tree species replace T. canadensis lost to invasive pests. A parallel experiment documented high mortality of B. trilobata (55%) when subjected to open canopy conditions similar to those resulting from selective “salvage” logging of hemlock in the region. These results indicate that the spread of exotic insect pests targeting T. canadensis is likely to produce strong indirect negative effects on the liverwort B. trilobata, via diminished commensal interactions with the conifer and increased amensalistic effects from the deciduous tree species that commonly replace it.

Anthropogenic environmental changes, or ‘stressors’, increasingly threaten biodiversity and ecosystem functioning worldwide. Multiple-stressor research is a rapidly expanding field of science that seeks to understand and ultimately predict the interactions between stressors. Reviews and meta-analyses of the primary scientific literature have largely been specific to either freshwater, marine or terrestrial ecology, or ecotoxicology. In this cross-disciplinary study, we review the state of knowledge within and among these disciplines to highlight commonality and division in multiple-stressor research. Our review goes beyond a description of previous research by using quantitative bibliometric analysis to identify the division between disciplines and link previously disconnected research communities. Towards a unified research framework, we discuss the shared goal of increased realism through both ecological and temporal complexity, with the overarching aim of improving predictive power. In a rapidly changing world, advancing our understanding of the cumulative ecological impacts of multiple stressors is critical for biodiversity conservation and ecosystem management. Identifying and overcoming the barriers to interdisciplinary knowledge exchange is necessary in rising to this challenge. Division between ecosystem types and disciplines is largely a human creation. Species and stressors cross these borders and so should the scientists who study them.

Bone morphogenetic protein 2 (BMP-2) is a potent inducer of osteoblast-mediated bone formation and is used in orthopaedic applications in humans. This study was performed to evaluate (1) recombinant human BMP-2 (rhBMP-2) in clinical cases of subchondral cystic lesion (SCL) in horses and (2) the osteoinductive effects of rhBMP-2 treatment in vitro on primary equine osteoblasts. Three horses with SCLs of the proximal interphalangeal (PIP) joint and associated lameness were treated by transcortical debridement and implantation of a collagen sponge containing rhBMP-2. In the in vitro studies, equine osteoblasts were cultured with rhBMP-2 to assess the effects of rhBMP-2 on their differentiation and mineralization. The treatment of SCLs with rhBMP-2 was well tolerated by all the horses, and improvements in subchondral bone radiographic appearance and lameness score were evident between 7 and 10 months post-surgery. Equine osteoblasts treated with rhBMP-2 demonstrated enhanced mineralization as evidenced by increases in Alizarin Red S staining. This was accompanied by significant increases in alkaline phosphatase (ALP) expression and activity, and a significant decrease in secreted osteocalcin levels. In conclusion rhBMP-2 can be used to assist in subchondral bone repair in horses, and we provide in vitro evidence to suggest that its influence on bone formation is mediated through enhanced osteoblast activity.

Climate change is leading to the global loss of open montane meadows by facilitating tree and shrub encroachment at high elevations. North America’s coastal mountains are particularly vulnerable to these changes, as they are relatively low elevation compared with interior mountains and contain only small areas of alpine tundra. We compared aerial photographs from 1962 with those from 2005 covering three subalpine regions on Vancouver Island, British Columbia, to document the extent of changes in woody vegetation and investigate associations between vegetation change and topography. Mean proportional woody vegetation cover increased significantly from 0.75±0.03 to 0.81±0.03 between 1962 and 2005 (p < 0.0001). Relative increase in woody vegetation cover was greater at higher elevations and on northerly aspects. These findings confirm an upward expansion and infilling of trees and shrubs and a reduction of the area encompassed by open alpine tundra on Vancouver Island. Loss of open meadow conditions at high elevations in this region will likely have consequences for alpine plant and animal communities.

Studies on resource sharing and partitioning generally consider species that occur in the same habitat. However, subsidies between linked habitats, such as streams and riparian zones, create potential for competition between populations which never directly interact. Evidence suggests that the abundance of riparian consumers declines after fish invasion and a subsequent increase in resource sharing of emerging insects. However, diet overlap has not been investigated. Here, we examine the trophic niche of native fish, invasive fish, and native spiders in South Africa using stable isotope analysis. We compared spider abundance and diet at upstream fishless and downstream fish sites and quantified niche overlap with invasive and native fish. Spider abundance was consistently higher at upstream fishless sites compared with paired downstream fish sites, suggesting that the fish reduced aquatic resource availability to riparian consumers. Spiders incorporated more aquatic than terrestrial insects in their diet, with aquatic insects accounting for 45–90% of spider mass. In three of four invaded trout rivers, we found that the average proportion of aquatic resources in web‐building spider diet was higher at fishless sites compared to fish sites. The probability of web‐building and ground spiders overlapping into the trophic niche of invasive brown and rainbow trout was as high as 26 and 51%, respectively. In contrast, the probability of spiders overlapping into the trophic niche of native fish was always less than 5%. Our results suggest that spiders share resources with invasive fish. In contrast, spiders had a low probability of trophic overlap with native fish indicating that the traits of invaders may be important in determining their influence on ecosystem subsidies. We have added to the growing body of evidence that invaders can have cross‐ecosystem impacts and demonstrated that this can be due to niche overlap.

The accelerating rate of global change has focused attention on the cumulative impacts of novel and extreme environmental changes (i.e. stressors), especially in marine ecosystems. As integrators of local catchment and regional processes, freshwater ecosystems are also ranked highly sensitive to the net effects of multiple stressors, yet there has not been a large-scale quantitative synthesis. We analysed data from 88 papers including 286 responses of freshwater ecosystems to paired stressors and discovered that overall, their cumulative mean effect size was less than the sum of their single effects (i.e. an antagonistic interaction). Net effects of dual stressors on diversity and functional performance response metrics were additive and antagonistic, respectively. Across individual studies, a simple vote-counting method revealed that the net effects of stressor pairs were frequently more antagonistic (41%) than synergistic (28%), additive (16%) or reversed (15%). Here, we define a reversal as occurring when the net impact of two stressors is in the opposite direction (negative or positive) from that of the sum of their single effects. While warming paired with nutrification resulted in additive net effects, the overall mean net effect of warming combined with a second stressor was antagonistic. Most importantly, the mean net effects across all stressor pairs and response metrics were consistently antagonistic or additive, contrasting the greater prevalence of reported synergies in marine systems. Here, a possible explanation for more antagonistic responses by freshwater biota to stressors is that the inherent greater environmental variability of smaller aquatic ecosystems fosters greater potential for acclimation and co-adaptation to multiple stressors.

Garra ghorensis is a small riverine cyprinid fish endemic to the southern Dead Sea that is endangered through habitat loss and invasive species. Here, their diet and trophic niche were assessed in three Jordanian populations: an allopatric population, a population sympatric with native Capoeta damascina and a population sympatric with invasive Oreochromis aureus. Stomach content analyses of samples collected between February 2011 and January 2012 revealed that detritus and algae were prominent food items in their diets, with low dietary contributions of animal material. The most frequent and abundant macro-invertebrates in intestines were Odonata nymphs and gastropod species. The calculation of trophic niche size from the stomach content data revealed that the niche of G. ghorensis (0.10) was generally smaller than sympatric C. damascina (0.24), with an overlap of 72%, whereas they had a larger trophic niche than sympatric O. aureus (0.20–0.13), with a niche overlap of 54%. These outputs were generally supported by stable isotope analyses of δ13C and δ15N completed on samples collected at the end of the 2011 growth season, although these indicated a greater contribution of animal material to assimilated diet. They also indicated that the trophic niche breadth [as standard ellipse area (SEA)] of C. damascina (4.18‰2) was higher than G. ghorensis (2.48‰2) and overlapped by 26%. For G. ghorensis, their SEA was slightly larger than O. aureus (4.33–4.00‰2), with an overlap of 27%. Although both methods indicated some sharing of food resources between sympatric fishes, there was no evidence suggesting detrimental outcomes for G. ghorensis and thus was not considered as a constraint on the status of their populations.

Considerable progress has been made in ecological and evolutionary genetics with studies demonstrating how genes underlying plant and microbial traits can influence adaptation and even 'extend' to influence community structure and ecosystem level processes. Progress in this area is limited to model systems with deep genetic and genomic resources that often have negligible ecological impact or interest. Thus, important linkages between genetic adaptations and their consequences at organismal and ecological scales are often lacking. Here we introduce the Sphagnome Project, which incorporates genomics into a long-running history of Sphagnum research that has documented unparalleled contributions to peatland ecology, carbon sequestration, biogeochemistry, microbiome research, niche construction, and ecosystem engineering. The Sphagnome Project encompasses a genus-level sequencing effort that represents a new type of model system driven not only by genetic tractability, but by ecologically relevant questions and hypotheses.

1. The trophic ecology of invasive species has important implications for their impacts on recipient ecosystems, with omnivorous invaders potentially affecting native species and processes over multiple trophic levels. The trophic ecology of invaders might be affected by both their body size and the characteristics of their habitat due to variation in energy requirements and resource availability.\ud 2. Here, using stable isotope analysis, we investigated the trophic ecology of the invasive crayfish Procambarus clarkii in 15 populations in Southwest France over a gradient of individual (crayfish body size), population (crayfish abundance) and ecosystem (lake size, productivity and predation pressure) characteristics. We predicted that population niche width, level of omnivory and trophic position of individuals would change with abiotic and biotic conditions but that these relationships would vary with lake size.\ud 3. The trophic position of individual crayfish increased with body size in lakes with low productivity, but decreased with body size in more productive lakes. As crayfish abundance increased (and therefore potential intraspecific competition), individual trophic position and population niche width decreased. This was most apparent in smaller lakes, suggesting it related to an increase in encounter rates with conspecifics.\ud 4. Body size, population abundance, lake size and lake productivity influenced the trophic ecology of invasive crayfish, which can affect their interactions with native species. Our results demonstrated that the trophic ecology of invasive species can be variable across invaded landscapes, with implications for their ecological impacts on native communities. This emphasises the importance of characterising the diet of invasive species across their non-native range and environmental gradients to better predict and manage their impacts.

Understanding how environmental variables and human disturbances influence the outcomes of introductions of non-native freshwater fish is integral to their risk management. This can be complex in freshwater ecosystems that receive subsidies that increase food availability, as these may influence the outcome of introductions through promoting the survival, reproduction and establishment of the introduced propagules through increasing their access to food resources. We determined how natural and/or artificial trophic subsidies affected the reproduction and establishment of the introduced topmouth gudgeon (Pseudorasbora parva) in replicated pond mesocosms. The mesocosms all started with eight mature fish and were run for 100 days during their reproductive season. The subsidies consisted of natural terrestrial prey and/or fishmeal pellets (a common trophic subsidy that can be significant in systems that are used as sport fisheries or for aquaculture). After 100 days, fish in the natural subsidy ponds showed minimal growth and very low reproductive output. Analysis of δC and δN indicated that their progeny, 0+ fish produced in the ponds, exploited the terrestrial prey. By contrast, in ponds where pellets were added, mineral nutrient availability and primary production were significantly increased, and the mature fish fed mainly on the aquatic resources. The increased productivity of the ponds significantly increased fish growth and fitness, resulting in high numbers of 0+ individuals that did feed on the pellets. Thus, subsidies that can increase both primary production and food resources (such as pelletised fishmeal) can significantly influence the ability of colonists to establish a population rapidly. Management efforts to minimise the risk of introductions should thus consider the role of these types of allochthonous subsidies. © 2013 The Authors. Freshwater Biology published by John Wiley & Sons Ltd.

When invasive species become integrated within a food web, they may have numerous direct and indirect impacts on the native community by creating novel trophic links, and modifying or disrupting existing ones. Here we discuss these impacts by drawing on examples from freshwater ecosystems, and argue that future research should quantify changes in such trophic interactions (i.e. the links in a food web), rather than simply focusing on traditional measures of diversity or abundance (i.e. the nodes in a food web). We conceptualise the impacts of invaders on trophic links as either direct consumption, indirect trophic effects (e.g. cascading interactions, competition) or indirect nontrophic effects (e.g. behaviour mediated). We then discuss how invader impacts on trophic links are context-dependent, varying with invader traits (e.g. feeding rates), abiotic variables (e.g. temperature, pH) and the traits of the receiving community (e.g. predators or competitors). Co-occurring invasive species and other environmental stressors, such as climate change, will also influence invader impacts on trophic links. Finally, we discuss the available methods to identify new food web interactions following invasion and to quantify how invasive species disrupt existing feeding links. Methods include direct observations in the field, laboratory trials (e.g. to quantify functional responses) and controlled mesocosm experiments to elucidate impacts on food webs. Field studies which use tracer techniques, such as stable isotope analyses, allow diet characterisation of both invaders and interacting native species in the wild. We conclude that invasive species often drastically alter food webs by creating and disrupting trophic links, and future research should be directed particularly towards disentangling the effects of invaders from other environmental stressors.

1.Invasive species are a key driver of global environmental change, with frequently strong negative consequences for native biodiversity and ecosystem processes.\ud Understanding competitive interactions between invaders and functionally similar native species provides an important benchmark for predicting the consequences of invasion. However, even though having a broad dietary niche is widely considered a key factor determining invasion success, little is known about the effects of competition with functionally similar native competitors on the dietary niche breadths of invasive species.\ud 2. We used a combination of field experiments and field surveys to examine the impacts of competition with a functionally similar native crab species on the population densities, growth rates and diet of the globally widespread invasive red swamp crayfish in an African river ecosystem.\ud 3. The presence of native crabs triggered significant dietary niche constriction within the invasive crayfish population. Further, growth rates of both species were reduced significantly, and by a similar extent, in the presence of one another. In spite of this,crayfish maintained positive growth rates in the presence of crabs, whereas crabs lost mass in the presence of crayfish. Consequently, over the three year duration of the study, crab abundance declined at those sites invaded by the crayfish, becoming locally extinct at one.\ud 4. The invasive crayfish had a dramatic effect on ecosystem structure and functioning, halving benthic invertebrate densities and increasing decomposition rates four-fold compared to the crabs. This indicates that replacement of native crabs by invasive crayfish likely alters the structure and functioning of African river ecosystems significantly.\ud 5. This study provides a novel example of the constriction of the dietary niche of a successful invasive population in the presence of competition from a functionally similar native species. This finding highlights the importance of considering both environmental and ecological contexts in order to predict and manage the impacts of\ud invasive species on ecosystems.

International audience; Brown trout Salmo trutta Linnaeus, 1758, is a priority species for conservation and management efforts in many European countries. In its native range, interactions with non-native fishes often adversely affect somatic growth rates and population abundances. Consequences of introduced North American pumpkinseed Lepomis gibbosus (Linnaeus, 1758) for native S. trutta were examined in stream stretches with and without L. gibbosus. Data for somatic growth rates and trophic niche breadth (using stable isotope analyses) provided little evidence of L. gibbosus presence being detrimental for S. trutta. Shifts in S. trutta diet at all sites were associated with increased piscivory with increasing body length, with no evidence to suggest that interspecific resource competition with L. gibbosus structured the food web or affected trophic positions. Three years later, and following L. gibbosus removal, data revealed slight shifts in the food web at each site, but these related to shifts in resources at the bottom of the food chain rather than a response to L. gibbosus removal. Consequently, the ecological consequences of L. gibbosus for S. trutta in the study stream were minimal, with S. trutta populations responding more to natural mechanisms regulating their populations than to the presence of this non-native fish species.

Biological monitoring has a long history in freshwaters, where much of the pioneering work in this field was developed over a 100 years ago—but few of the traditional monitoring tools provide the global perspective on biodiversity loss and its consequences for ecosystem functioning that are now needed. Rather than forcing existing monitoring paradigms to respond to questions they were never originally designed to address, we need to take a step back and assess the prospects for novel approaches that could be developed and adopted in the future. To resolve some of the issues with indicators currently used to inform policymakers, we highlight new biological monitoring tools that are being used, or could be developed in the near future, which (1) consider less-studied taxonomic groups, (2) are standardised across regions to allow global comparisons, and (3) measure change over multiple time points. The new tools we suggest make use of some of the key technological and logistical advances seen in recent years—including remote sensing, molecular tools, and local-to-global citizen science networks. We recommend that these new indicators should be considered in future assessments of freshwater ecosystem health and contribute to the evidence base for global to regional (and national) assessments of biodiversity and ecosystem services: for example, within the emerging framework of the Intergovernmental Platform on Biodiversity and Ecosystem Services.

Stable isotope analysis is an important tool for characterising food web structure; however, interpretation of isotope data can often be flawed. For instance, lipid normalisation and trophic fractionation values are often assumed to be constant, but can vary considerably between ecosystems, species and tissues. Here, previously determined lipid normalisation equations and trophic fractionation values were re-evaluated using freshwater fish species from three rivers in the Upper Zambezian floodplain ecoregion in southern Africa. The parameters commonly used in lipid normalisation equations were not correct for the 18 model species (new D and I parameters were estimated as D = 4.46‰ [95% CI: 2.62, 4.85] and constant I = 0 [95% CI: 0, 0.17]). We suggest that future isotopic analyses on freshwater fishes use our new values if the species under consideration do not have a high lipid content in their white muscle tissue. Nitrogen fractionation values varied between species and river basin; however, the average value closely matched that calculated in previous studies on other species (δ15N fractionation factor of 3.37 ± 1.30 ‰). Here we have highlighted the need to treat stable isotope data correctly in food web studies to avoid misinterpretation of the data.

Societies' growing global footprint is causing a rapid increase in the demand for natural resources (i.e. ecosystem services), while also reducing the capacity of ecosystems to provide them. Freshwater ecosystems contribute disproportionately to ecosystem services but are also particularly vulnerable to global environmental change. The provisioning of freshwater services, such as water and food production, is especially important in developing countries. Here, we review the evidence which demonstrates the impacts of key environmental stressors on these two important provisioning services in southern Africa. Land use change, species invasions and climate change can all be linked to a loss of the provisioning services provided by freshwater ecosystems in southern Africa. Water resources for drinking, agriculture, sanitation and power are expected to decline as a result of both climate and land use change. Fish production may be negatively or positively affected by the different stressors, highlighting the high context-dependency associated with their impacts. Evidence also suggests that these stressors can interact to alter one another's impacts or promote the proliferation of further stressors. For instance, land use change can promote aquatic plant invasions and, subsequently, the stressors may interact synergistically to cause fish kills. Stressors may also interact to mitigate one another's impact, for instance fish invasions may enhance total fish catch following a pollution event. Since stressors are unlikely to occur in isolation and multiple stressors frequently result in complex ‘ecological surprises’, it is urgent that we increase research effort on the links between multiple stressors and the loss of ecosystem services. Future research should, therefore, focus on the combined impacts of multiple environmental, social, and economic stressors on natural resources and provisioning ecosystem services in southern Africa.