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Wetland connectivity: understanding the dispersal of organisms that occur in Victoria’s wetlands draft


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Overview and objectives


Biological connectivity broadly refers to the ability of plants and animals to move among habitat patches in the landscape (Hanski 1998, Tischendorf and Fahrig 2000). Understanding connectivity is of fundamental importance because it underlies landscape-scale ecological processes such as species invasion, immigration and metacommunity dynamics (Nathan and Muller-Landau 2000, Hubbell 2001, Wright et al. 2003, Leibold et al. 2004). Increasing recognition of the ecological significance of dispersal in maintaining species diversity has highlighted the need to consider connectivity in conservation planning. The conservation of biodiversity has been addressed in the past through a system of protected areas, but only 6–12% of land area, both in Australia and globally, is protected (Soulé et al. 2004, Mackey et al. 2007). The existing area of reserves is considered 5–10% too small and the biological connections among them inadequate to prevent species extinctions, the rate of which has been estimated to be 1000–10 000 times higher than natural (Soulé et al. 2004).

In response, there has been a shift towards developing conservation programs that interconnect core reserves, and that manage the intervening landscape in ways that assist the movement of organisms (Amezaga et al. 2002, Soulé et al. 2004, DSE 2010). Such initiatives require an understanding of the processes that connect habitats. Assessing biological connectivity requires a species-level approach that identifies how the spatial and temporal characteristics of the environment interact with an organism’s dispersal biology to impede or facilitate movement among habitat patches (Taylor et al. 1993).



Our understanding of biological connectivity has been developed in terrestrial systems, particularly in fragmented forests and woodland habitats, and the processes that connect aquatic systems are less understood (Weins 2006, Doerr et al. 2010). The broad purpose of this report is to assess the processes that biologically connect wetland habitats. This information may be used to guide the development of landscape-scale maps of potential wetland connectivity for key groups of aquatic organisms in Victoria. Understanding the connectivity of Victoria’s wetlands will assist the landscape-scale management of aquatic habitats by identifying:

  • wetlands that are biologically linked and form functional mosaics

  • bottlenecks in the movement of taxa among core habitats

  • wetlands that act as stepping stones, permitting the exchange of plants and animals among many wetlands

  • whether a loss in connectivity could be contributing to poor wetland condition

  • sites for habitat restoration or creation that will have flow-on benefits because they allow dispersal to other habitats

  • pathways for the invasion of introduced species.

This report provides a general background of landscape connectivity and its importance in understanding the spatial distribution of species. The significance of connectivity in aquatic habitats is then examined, and approaches to measuring dispersal are summarised. The dispersal of key groups of wetland organisms is then described, including invertebrates, amphibians, fish, plants and waterbirds. For each group the objective has been to identify, where possible:

  • patterns of habitat utilisation

  • the mode(s), scale, and pattern of dispersal in the landscape

  • landscape barriers to dispersal

  • evidence that supports the ecological significance of dispersal.

Finally, key modelling approaches to assess connectivity at a landscape-scale are described, which — along with the dispersal biology of the focal groups — can inform the development of maps that represent potential connectivity among wetlands.
  1. Landscape connectivity

    1. What is connectivity?


Connectivity broadly refers to the ability of plants and animals to move among habitat patches in the landscape (Hanski 1998, Tischendorf and Fahrig 2000). A distinction is often made between structural and biological connectivity. Structural connectivity describes the physical elements of the landscape that influence species distributions, including the size and configuration of habitat patches in the landscape, the distances among habitats, and sometimes the nature of the intervening landscape. Biological connectivity considers whether species can navigate the landscape to access suitable habitat patches. It does this by considering the mobility of an organism and the characteristic of the landscape that favour or limit movement. Species vary in their mobility and how they respond to the landscape, and this produces different rates, patterns and scales of biological connectivity in the landscape (Taylor et al. 1993).

Our ability to directly assess the movement of an organism between habitats — ‘actual connectivity’ — requires a study of movement or genetics. Such studies are uncommon, so ‘potential connectivity’ is usually inferred from knowledge of the species’ mobility and the nature of the landscape. This approach requires and understanding of the processes that shape patterns of dispersal, including the following (Tischendorf and Fahrig 2000):



  • species abundance, which influences the number of individuals dispersing

  • the number, area and arrangement of habitat patches in the landscape

  • mode(s) of dispersal (e.g. wind, water, animal vectors)

  • spatial patterns of movement (e.g. prevailing winds that disperse seeds)

  • scales of movement of the organisms being studied

  • features of the landscape between habitats that may facilitate or impede dispersal

  • temporal patterns in the availability and behaviour of dispersal vectors (e.g. floods), or in the movement behaviour of an organism (e.g. seasonal movements associated with breeding or moulting in waterbirds)

  • mortality risks associated with movement.
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