Archive for the ‘Australia’ Category

Focus on the process! That’s what restoring ecosystems means, and needs.

Friday, August 31st, 2012

In 2011, Australian ecologists David J. Tongway and John A. Ludwig, published a grand summary of their multiple years of on-the-ground experience of restoring disturbed landscapes and ecosystems. Using examples from restoration works on mine sites, road verges, rangelands, and farmland they illustrate how their function-based approach plays out.

The book, “restoring disturbed landscapes – putting principles into practice“, published by Island Press, is a very accessible introduction to the Ecosystem Function Analysis method developed by CSIRO.

One of their main ideas is that restoring degraded ecosystems first requires that the problematic physical (abiotic) processes be solved: the negative effects of topography on water and material flows must be mitigated before self-sustaining biological processes can play their part (e.g. vegetation, grazing regimes, etc.).

First, solve the underlying physical processes! No point in planting your favourite flower here…

Of course, they also remind us that restoration must be framed and carried out in an adaptive management feedback loop where the ecosystem or landscape’s trajectory is monitored and compared to reference conditions. The book is a nicely illustrated reminder of these good practices…

In the context of mitigation requirements for development impacts on biodiversity, the following quote summarizes nicely one of their main points:

switching from simply observing the presence, absence, or abundance of organisms to assessing the status of functional processes in an explicitly spatial (landscape) context is as challenging as venturing into previously uncharted waters. (…) Being able to “read the landscape” is a rare and valuable asset.

The principle of habitat substitutability

Monday, November 14th, 2011

Biodiversity offsets, whether they focus on species (and their habitat requirements), habitat types, ecosystem properties or ecosystem services, are all based on the idea that the elements they target are – to a degree – substitutable: e.g. the breeding habitat of a particular bird species here can be substituted by an “equivalent” habitat somewhere else.

In an interesting article*, recently in-press in Biodiversity & Conservation, Kate Sherren and her former colleagues at ANU present survey results on how land-holders in rural Australia view the substitutability of different arrangements of trees and woodlands on their properties. This can be very important for aligning conservation policy such as offset schemes with the values and experience of the people they target.

The rationale for the survey is that at the farm level, substitutions between these elements are made daily, albeit at a small scale: a patch is planted, scattered trees are cut-down etc. These decisions could reveal farmer’s views on their value and their substitutability. The survey found that farmers could be divided into three groups:

  • Farmers, mainly older and less educated, who valued a “tidy” farm but did not care for the specific arrangements of trees and woodlands
  • Farmers who strongly supported the need for a diversity of tree cover arrangements on their land. Because of limited financial or time resources, these views were only rarely translated into concrete action.
  • Farmers who preferred woodlands and connective strips over scattered trees. This group included those that also crop their land using machinery.
  • What can be done with this knowledge? Well, the authors argue that the main risk with widespread offsetting schemes is that tree cover arrangements will homogenize, towards wooded paddocks that are easier to create, maintain, monitor etc. This could have unintended consequences in terms of landscape-level heterogeneity in habitat for species or ecosystem services, especially those related to scattered trees.

    Scattered trees in Australia

    To avoid this homogenization, specific policies could be devised that target the first two types of land-holders, to get them to increase heterogeneity on their land.

    This could be done by allowing land-holders to actively suggest measures in favour of tree cover (and bid for funding) such as “crash grazing”, adding coarse woody debris, weed control or planting of under-storey species… These different measures are conducive to improving the “quality” of existing woodland rather than focusing on area-based measures such as grazing exclusion which could tend to homogenize the landscape and have the major caveat of taking land out of production which could be called into question in the long-term.

    Measures targeting the management of existing trees and woodlands also have drawbacks. The main one is how long-lasting they can be made, and thus how long the binding contracts have to be made. The USDA’s Conservation Reserve Program is one long-lasting program that can provide inspiration for such renewable management-based contracts with land-holders.

    The Conservation Reserve Program - a long-lasting contract-based PES scheme

    Another difficulty with management based measures such as those outlined above is measuring the actual “gain” they generate, so that they can be sized adequately to offset impacts elsewhere. This probably requires a conservative approach – i.e. over-sizing of offsets – as well as further research on baseline trends and short- and long-term effects of these management changes.

    * Sherren K., Yoon H-J., Clayton H. & Schirmer J. (2011): Do Australian graziers have an offset mindset about their farm trees? Biodiversity & Conservation, in press.

    On time-lags and location selection in offsets

    Monday, October 10th, 2011

    Ascelin Gordon and his colleagues from Melbourne recently went through an interesting modelling exercise. They modelled the long-term effects, in both space and time, of different offset policies concerning urban development impacts on native grasslands around the city.

    Their modelling explicitly included uncertainties , following the approach described by Langford et al. (2009). These uncertainties were both ecological (edge effects on conservation value, grassland response to management and offsetting, etc.) and political: which offset policy?

    They compared five different offset policies:

  • No change
  • Development without offsets
  • Non strategic offsets (wherever, whenever)
  • Strategic offsets (offsets are located together, in designated areas)
  • Strategic immediate offsets (offsets are effective at the start of simulations, a.k.a. habitat banking)
  • Their conclusions are that offset policies that include spatial and temporal constraints on offsets give the best conservation outcomes. They also point out the obvious: the selection of the baseline is central to any assessment of policy outcomes.

    whether (or when) [policies] achieve the objective of a “net gain” completely depends on the choice of baseline.

    It might be obvious but it is certainly tricky when looking at policies that involve long-term ecological dynamics…

    To find out more, check out their paper in Environmental Modelling & Software*. A pdf can be downloaded here.

    * Gordon A., Langford W.T., Todd J.A., White M.D., Mullerworth D.W. & Bekessy S.A. (in press): Assessing the impacts of biodiversity offset policies. Environmental Modelling & Software, in press.