Turning up the heat on freshwater interactions

Riparian restoration mitigates the impacts of climate change

DPoint78_Page_01_Image_(13) Freshwater habitats are critically important for a broad range of animals and plants (see the article, ‘the importance of freshwater habitat’) and they are in trouble. Worldwide these habitats are experiencing declines in biodiversity far greater than those being experienced in other terrestrial and marine ecosystems. New research involving EDG modelling is hoping to help managers identify how this decline might be best dealt with. The problems confronting freshwater habitats are many. The combined and interacting influences of multiple stressors in freshwater ecosystems have resulted in population declines and range reductions of freshwater species all around the world. Yet, our understanding of the combined effects of climate change and landuse change on freshwater biodiversity is limited. For example, large uncertainties remain regarding which processes (eg, biophysical processes such as water temperature or nitrogen enrichment) will have the greatest impact on biodiversity in freshwater ecosystems and whether the sum of the individual stressor effects are greater than any stressor alone (ie, a synergistic interaction).

“High nutrients and high runoff resulting from urbanization interacted with high nutrients and high water temperature as a result of climate change. This was the leading driver of potential declines in macroinvertebrates and fish at finer scales. ”

Working with UQ, CSIRO, Griffith University and the Queensland Government, EDG researchers modelled the independent and combined effects of climate change and land-use change on freshwater macroinvertebrates and fish using South East Queensland and the Ecosystem Health Monitoring Program as a case study (Mantyka-Pringle et al. 2014). The first step was building a conceptual model to identify the major causal links between landuse (ie, the amount of hard impervious surfaces and the amount of riparian vegetation) and climate (ie, air temperature, precipitation and rainfall variability) on freshwater biodiversity (see figure 1). The scientific literature identifies nitrogen, phosphorus, runoff and water temperature as among the most important drivers of biodiversity loss in freshwater habitat. These were included as variables in the conceptual model. Elevation was also included because it is an important natural determinant for predicting macroinvertebrate and fish distributions. The team then used this conceptual model to build a Bayesian Belief Network. This was parameterized using current land-use and climatic conditions and enabled the researchers to predict the effect of future land-use and climate change on the richness of macroinvertebrates and fish. They discovered little change in species richness averaged across catchments, but identified important impacts and effects at the finer scale. High nutrients and high runoff resulting from urbanization interacted with high nutrients and high water temperature as a result of climate change. This was the leading driver of potential declines in macroinvertebrates and fish at finer scales. This is the first study to separate out the constituent drivers of impacts on biodiversity that result from climate change and land-use change.

Figure 1: A conceptual model of the key climate, land-use and water quality variables that interact and impact macroinvertebrate and fish richness in the freshwater habitat being considered. A solid arrow indicates a positive effect or link, whereas a closed circle indicates a negative effect or link. (See Mantyka-Pringle et al., 2014 for more details.)

Figure 1: A conceptual model of the key climate, land-use and water quality variables that interact and impact macroinvertebrate and fish richness in the freshwater habitat being considered. A solid arrow indicates a positive effect or link, whereas a closed circle indicates a negative effect or link. (See Mantyka-Pringle et al., 2014 for more details.)

By identifying the mechanisms behind predicted biodiversity loss, the researchers were able to identify management strategies that can simultaneously tackle both climate change and landuse change. The good news coming out of this study was that the restoration of riparian vegetation was identified as an important tool for adaptation that can mitigate the negative effects of climate change and land-use change on freshwater biota. In Australia and elsewhere, riparian restoration management has been transformed over the last few decades from engineer-based to ecosystem-based approaches. As a result, planting of native riparian buffers has become a priority for restoration projects as it improves ecological conditions within streams without negatively impacting riparian soils. DPoint78_Page_01_Image_(18) More info: Chrystal Mantyka-Pringle c.mantykapringle@uq.edu.au Reference Mantyka-Pringle CS, TG Martin, DB Moffatt, S Linke & JR Rhodes. (2014) Understanding and Predicting the Combined Effects of Climate Change and Land-Use Change on Freshwater Macroinvertebrates and Fish. Journal of Applied Ecology doi: 10.1111/1365-2664.12236

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