Climate change effects on upland stream macroinvertebrates over a 25-year period

Climate change effects on some ecosystems are still poorly known, particularly where they interact with other climatic phenomena or stressors. We used data spanning 25 years (1981–2005) from temperate headwaters at Llyn Brianne (UK) to test three hypotheses: (1) stream macroinvertebrates vary with winter climate; (2) ecological effects attributable to directional climate change and the North Atlantic Oscillation (NAO) are distinguishable and (3) climatic effects on macroinvertebrates depend on whether streams are impacted by acidification. Positive (i.e. warmer, wetter) NAO phases were accompanied by reduced interannual stability (=similarity) in macroinvertebrate assemblage in all streams, but associated variations in composition occurred only in acid moorland. The NAO and directional climate change together explained 70% of interannual variation in temperature, but forest and moorland streams warmed respectively by 1.4 and 1.7°C (P<0.001) between 1981 and 2005 after accounting for NAO effects. Significant responses among macroinvertebrates were confined to circumneutral streams, where future thermal projections (+1, +2, +3°C) suggested considerable change. Spring macroinvertebrate abundance might decline by 21% for every 1°C rise. Although many core species could persist if temperature gain reached 3°C, 4–10 mostly scarce taxa (5–12% of the species pool) would risk local extinction. Temperature increase in Wales approaches this magnitude by the 2050s under the Hadley HadCM3 scenarios. These results support all three hypotheses and illustrate how headwater stream ecosystems are sensitive to climate change. Altered composition and abundance could affect conservation and ecological function, with the NAO compounding climate change effects during positive phases. We suggest that acidification, in impacted streams, overrides climatic effects on macroinvertebrates by simplifying assemblages and reducing richness. Climatic processes might, nevertheless, exacerbate acidification or offset biological recovery.     

Non-native freshwater fishes in Norway: history, consequences and perspectives

At present, there are 43 self-sustaining fish species in Norwegian fresh waters, 11 (26%) of which are non-native, representing four families (Salmonidae, Cyprinidae, Centrarchidae and Ictaluridae). Human-mediated fish introductions probably began in the 15th century with common carp Cyprinus carpio, but most have occurred between the late 1800s and late 1900s. The number of known established populations varies from one (goldfish Carassius auratus ) to nearly 250 (tench Tinca tinca ). Dispersal risk is also highest with tench, which is being spread by anglers for its appeal as a trophy fish. Intentional introductions to improve amenity angling have been part of fisheries management programmes ( e.g. brook trout Salvelinus fontinalis ), so this appears to be an increasingly common introduction vector despite the prohibition under legislation of introducing any species of non-native fishes. Some introduced species, such as brook trout, have declined in abundance and number of populations as the quality of acidified waters has been restored, being replaced by native brown trout Salmo trutta . Further range expansion by some species ( e.g. common carp, goldfish and pumpkinseed Lepomis gibbosus ) is probably restricted by current climatic conditions.     

Perturbation,Restoration and Seeking Ecological Sustainability in Australian Flowing Waters

It is now accepted that most of the rivers and streams of Australia have been degraded to varying extents by European settlement. The scale and level of this degradation have been documented by State and Federal government authorities. To halt and reverse the degradation in the next two decades, it is crucial that the conservation and restoration of streams, rivers, riparian zones, and catchments become paramount in land and water management. Effective stream restoration requires a coordinated effort at the catchment level rather than at the level of many individual local sites. Monitoring, including the gathering of before-restoration data, and the setting of feasibly-attainable goals are key components of effective restoration. In planning projects and setting goals, it needs to be recognized that some goals may only be attained in the long-term. Large-scale restoration projects will require partnerships to be formed between resource managers and scientists, with other stakeholders possibly involved. Selected projects could be adaptively managed with the emphasis on gaining scientific knowledge on the effects of management interventions.     

To Be Or Not to Be? Variable selection can change the projected fate of a threatened species under future climate

Species distribution models (SDMs) are commonly used to project future changes in the geographic ranges of species, to estimate extinction rates and to plan biodiversity conservation. However, these models can produce a range of results depending on how they are parameterized, and over‐reliance on a single model may lead to overconfidence in maps of future distributions. The choice of predictor variable can have a greater influence on projected future habitat than the range of climate models used. We demonstrate this in the case of the Ptunarra Brown Butterfly, a species listed as vulnerable in Tasmania, Australia. We use the Maxent model to develop future projections for this species based on three variable sets; all 35 commonly used so‐called ‘bioclimatic’ variables, a subset of these based on expert knowledge, and a set of monthly climate variables relevant to the species’ primary activity period. We used a dynamically downscaled regional climate model based on three global climate models. Depending on the choice of variable set, the species is projected either to experience very little contraction of habitat or to come close to extinction by the end of the century due to lack of suitable climate. The different conclusions could have important consequences for conservation planning and management, including the perceived viability of habitat restoration. The output of SDMs should therefore be used to define the range of possible trajectories a species may be on, and ongoing monitoring used to inform management as changes occur.     

Restoration principles emerging from one of the world's largest tidal marsh restoration projects

One of the world's largest tidal wetland restorationprojects was conceived to offset the loss of nekton toonce-through cooling at a power plant on Delaware Bay,USA. An aggregated food chain model was employed toestimate the area of tidal salt marsh required toreplace these losses. The 5040 ha was comprised of twodegraded marsh types – Phragmites- dominatedmarshes and diked salt hay farms – at elevenlocations in oligo-mesohaline and polyhaline reachesof the estuary. At a series of summits convened withnoted experts in the field, it was decided to apply anecological engineering approach (i.e., self design,and minimal intrusion) in a landscape ecologyframework to the restoration designs while at the sametime monitoring long-term success of the project inthe context of a bound of expectation. The latterencompassed a range of reference marsh planforms andacceptable end-points established interactively withtwo advisory committees, numerous resource agencies,the permitting agency and multiple-stakeholder groups.In addition to the technical recommendations providedby the project's advisors, public health and safety,property protection and public access to the restoredsites were a constant part of the dialogue between theutility, its consulting scientists and theresource/permitting agencies. Adaptive management wasused to maintain the restoration trajectories, ensurethat success criteria were met in a timely fashion,and to protect the public against potential effects ofsalt intrusion into wells and septic systems, andagainst upland flooding. Herbicide spray, followed byprescribed burns and altered microtopography were usedat Phragmites-dominated sites, and excavation ofhigher order channels and dike breaching were themethods used to initiate the restorations at the dikedsalt hay farms. Monitoring consisted of evaluating therate of re-vegetation and redevelopment of naturaldrainage networks, nekton response to therestorations, and focused research on nutrient flux,nekton movements, condition factors, trophic linkages,and other specific topics. Because of its size anduniqueness, the Estuary Enhancement Program as thisproject is known, has become an important case studyfor scientists engaged in restoration ecology and theapplication of ecological engineering principles. Thehistory of this project, and ultimately theRestoration Principles that emerged from it, are thesubjects of this paper. By documenting the pathways tosuccess, it is hoped that other restoration ecologistsand practitioners will benefit from the experiences wehave gained.