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River corridors

  River corridors
 

Full Title

The role of rivers, floodplains and associated wetlands in a broader landscape scale approach to wildlife corridors.

Contact Person 

Rick Stoffels

Funding Body

Department of the Environment

National Environmental Research Program

Duration

May 2013 to May 2014

Collaborators

CSIRO, Murray CMA, NSW Office of Environment and Heritage, MDBA

Summary

The movement of biota is fundamental to the persistence of species and maintenance of biodiversity.  The importance of movement is even greater in highly dynamic ecosystems such as rivers and their associated wetlands and floodplains where cycles of wetting and drying create a shifting habitat mosaic.  One of the major consequences of agricultural development is the fragmentation of river ecosystems either through the construction of barriers (dams, weirs and levies), changes in flow regimes that change hydrological connectivity or vegetation clearing that creates isolated patches of habitat.  The restoration of connectivity in river-floodplain ecosystems is complicated by both the variety of changes to connectivity and the dynamic and diverse character or these systems.

The protection and restoration of the environmental values of river ecosystems will depend on ensuring the capacity of species to disperse.  There are currently management initiatives seeking to address the three major impacts of fragmentation of river ecosystems:

  • The installation of fish-ways, such as the Hume to the Sea fish-way project, seeks to improve fish dispersal.
  • The Basin Plan will rehabilitate patterns of hydrological connectivity through the management of environmental flows.
  • The National Wildlife Corridors Plan seeks to ensure landscape corridors are available to support movement and dispersal. 

The success of all these initiatives relies on our understanding of the movement of biota and the consequences of changes in dispersal to the persistence and distribution of populations and the diversity of ecosystems.

While fragmentation is likely to be one of the significant drivers of decline in the condition of river-floodplain ecosystems, the restoration of connectivity is associated with some significant risks.  In some instances, limits on dispersal were important to sustaining biodiversity.  Examples include frogs and macroinvertebrates such as shield shrimp that rely on limited fish dispersal to ensure predator free habitats in which to complete their life cycle.  A second risk emerges from the spread of invasive species.  In some instances, improving connectivity among components of a system can facilitate the dispersal of invasive species to the detriment of indigenous biota.  Finally, restoring connectivity may result in fluxes of material that may damage receiving systems.  Examples include large amounts of dissolved organic matter and high sediment loads.

Because dispersal has been affected by several interacting stressors (barriers, flows and vegetation), it is probable that all three stressors will need to be addressed.  But given the complex nature of river-floodplain ecosystems, and the risks associated with restoration it is important that the restoration activities are complementary and based on our understanding of the movements required to sustain species within a dynamic landscape.  It will also be important to understand the risks so that informed trade-offs can be made and actions undertaken to reduce the likelihood or consequences of known risks.

Objectives

The general objective underlying this project is to improve our understanding of how riverine corridors affect the maintenance of freshwater and riparian biodiversity at multiple spatial and temporal scales. Specifically, we have two broad objectives:

  • First, we aim to develop conceptual frameworks that outline how the ‘local’ processes of biodiversity maintenance interact with organism dispersal through riverine corridors to maintain biodiversity at ‘regional’ scales. The focus will be on freshwater and riparian biodiversity within the Murray-Darling Basin.
  • Second, we aim to assess the level of corridor and habitat fragmentation within the Murray-Darling Basin, and in light of the conceptual frameworks we develop, ask: what are the potential consequences of this fragmentation to biodiversity maintenance, and how can we better manage corridors to restore biodiversity and build resilience?