The effects of climatic fluctuations and extreme events on running water ecosystems.
Most research on the effects of environmental change in freshwaters has focused on incremental changes in average conditions, rather than fluctuations or extreme events such as heatwaves, cold snaps, droughts, floods or wildfires, which may have even more profound consequences. Such events are commonly predicted to increase in frequency, intensity and duration with global climate change, with many systems being exposed to conditions with no recent historical precedent. We propose a mechanistic framework for predicting potential impacts of environmental fluctuations on running-water ecosystems by scaling up effects of fluctuations from individuals to entire ecosystems. This framework requires integration of four key components: effects of the environment on individual metabolism, metabolic and biomechanical constraints on fluctuating species interactions, assembly dynamics of local food webs, and mapping the dynamics of the meta-community onto ecosystem function. We illustrate the framework by developing a mathematical model of environmental fluctuations on dynamically assembling food webs. We highlight (currently limited) empirical evidence for emerging insights and theoretical predictions. For example, widely supported predictions about the effects of environmental fluctuations are: high vulnerability of species with high per capita metabolic demands such as large-bodied ones at the top of food webs; simplification of food web network structure and impaired energetic transfer efficiency; and reduced resilience and top-down relative to bottom-up regulation of food web and ecosystem processes. We conclude by identifying key questions and challenges that need to be addressed to develop more accurate and predictive bio-assessments of the effects of fluctuations, and implications of fluctuations for management practices in an increasingly uncertain world.
Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK.
Guy
G
Woodward
Group de Recerca Freshwater Ecology and Management (FEM), Departament d'Ecologia, Facultat de Biologia, Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona (UB), Diagonal 643, Barcelona, Catalonia, 08028, Spain.
Núria
N
Bonada
School of Geography and Water, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.
Lee E
LE
Brown
Institute of Agriculture and Environment-Ecology, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand.
Russell G
RG
Death
Water Research Institute and Cardiff School of Biosciences, Cardiff CF10 3AX, UK.
Isabelle
I
Durance
Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK.
Clare
C
Gray
School of Biological Sciences, Monash University, Clayton, Melbourne, Victoria 3800, Australia.
Sally
S
Hladyz
School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Mark E
ME
Ledger
School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
Alexander M
AM
Milner
Water Research Institute and Cardiff School of Biosciences, Cardiff CF10 3AX, UK.
Steve J
SJ
Ormerod
Institute for Applied Ecology, University of Canberra, Australian Capital Territory 2601, Australia.
Ross M
RM
Thompson
Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK s.pawar@imperial.ac.uk.
Samraat
0000-0001-8375-5684
S
Pawar
D057231:Climate Change; D017753:Ecosystem; D020387:Food Chain; D008954:Models, Biological; D045483:Rivers
biodiversity; community assembly; ecosystem functioning; food webs; metabolism; resilience