Cons Rest


1) Changes to natural environments of arable areas of southern Australia. Overview and prognosis for how these areas will change in the future

  • Extensive habitat modification since colonisation, especially vegetation clearance.
  • Introduction of ungulates
  • Many European plants were introduced. These have had a prolonged exposure to humans and are likely to be resilient to disturbances and can outcompete native plants in many cases.
  • Arable parts of the environment were disproportionately affected
  • Use of land for mining, urban and transport, agriculture, forestry, grazing.
  • Hunting and predation of native animals by introduced species.
  • Extensive fragmentation leading to a loss of connectivity, preventing dispersal and gene flow. Increase in edge effects.
  • Reduction in habitat means less area for animals. Fewer species using patches. Reductions in the numbers of organisms per unit area. Extinction debt concept.
  • Movement between patches and how these are disrupted by vegetation clearance is not well quantified.
  • Some native species are favoured - eg extensive grasslands and removal of dingos increased kangaroos. Possums and noisy miners in urban areas.
  • Reduction in populations increase chance of extinction by demographic (eg chance of all females dying in one year) and genetic malfunctions (inbreeding, outbreeding depression)
  • In future - species loss is likely to continue due to extinction debt. Can be reduced to some degree by stopping habitat destruction and increasing available habitat now.
  • Chance and extent of recovery depends on how disturbed it is now. Removal, replacement, utilisation?

2 a) Mercurial sun orchid

  • Orchids have very specific pollinators. Examine what is visiting plants in site where seed set occurs and if it is present elsewhere. What other resources or habitats do those pollinators use that aren't present elsewhere?
  • Are any competitors to pollinators present? In non-orchid flowers, may be competing for nectar resources.. could be competing for habitat instead.
  • Pollinator limitation can be tested by manual pollination.
  • Could also test nutrient status - being on road-side could cause toxic effects.
  • Could compare genetic diversity between sites to see if plants not setting seed setting site are suffering from inbreeding depression??

2 b) Local provenance

  • Text-book reason: the claimed importance of conserving locally adapted genotypes, which are assumed to show high fitness.
  • Destruction of interesting genetic information on the past history of a local populatiohn
  • Could also lose fitness through epistasis, the disruption of co-adapted gene complexes
  • May not be particularly relevant if past or future climatic change is faster than evolution of those species.
  • Microclimates within one site can vary considerably. How local should provenance be?
  • Long-lived trees may have germinated in very different conditions. In what sense are their seeds locally adapted now?
  • Is it only important for relatively short-lived plants? In particularly unusual environments?
  • Natural selection should remove unfit hybrids, though a large number of introduction events may shift this.
  • Genetic and geographical distance aren't necessarily correlated

3) Hooded robins

  • Food availability can be tested by examining proportion of time spent foraging
  • The effect of weed invasion on foraging success could be assessed using experiments where food is placed at various distances from nest and the ability of birds to spot it assessed in habitats with and without weeds.
  • Predation could be attributed to edge effects - does it seem to vary with location within habitats?
  • Could also be due to patch size - compare success in large vs small patches
  • Test predation of fake eggs

5) Revegetation programs


  • Most aren't on a very large scale. Don't approach structure of natural systems - eg planting density, matrix of age classes, understorey, shape of trees.
  • eg too dense leads to trees with few lateral branches - poor for insectivorous birds that perch just above the ground etc
  • Often conducted on poor quality land retired from farms
  • Lack of connectivity to remnant vegetation
  • Sometimes use species that aren't native to an area


  • Considering local provenance
  • Using different planting treatments to work out what is effective.. can lead to the best conditions being found, and also produce more heterogeneous environment.


  • Do plants flower? Set seed? Are seeds viable? Dispersed to suitable germination sites? Do they survive to germinate? Do the seedlings survive? Do the saplings?
  • Wind speeds reduced?
  • Should also conduct assessments at a regional scale. Increasing summer-autumn floral resources may increase the seed production of winter flowering lants that were severely pollinator limited in nearby sites.
  • Water table reduced?

6) Tammar Wallabies (and any mammals on offshore islands, 2005 q6)

  • Have predators been removed from mainland? Completely? Several programs have failed even after intensive baiting.
  • Will local provenance be important?
  • Suitable habitat available? If not, should it be re-established first?
  • Assess survival of reintroduced over time - do they have enough to eat, are they being eaten etc?
  • How many individuals should be moved? Maximum 10% of the source population? 50? 500? (minimum viable population)
  • Age and sexes to be moved? Established or non-established pairs (if applicable)?
  • Timing - move post-breeding? Immediately prior to breeding? Not at a stressful time of the year?
  • One or several releases?
  • Hard or soft release?
  • Monitoring at source and receipt sites. Survival and breeding performance, and recruitment into vacant areas at source.

= 2004 =

2) Woodland birds decline

  • Habitat destruction, predation (direct and nest), past extinction debt, lack of food resources, loss of connectivity between populations due to fragmentation, loss of habitat due to competition (eg for hollows)

3) Bumblebees


  • May out-compete and exclude native pollinators
  • May not pollinate effectively due to strategy or fidelity and lower seed production.
  • Likely to be very adaptable to many parts of mainland. Definitely won't be specific to target plant.
  • Densities in Tasmania are relatively high and may be large enough to make them significant on ecosystem processes.
  • Suffer little predation
  • Abundance peak coincides with that of other insect pollinators. Also present at most times of the year, though.
  • Compare levels of seed set and gene flow in presence and absence of bumblebees
  • Cointroduction of pathogens that may affect native species
  • 'Sleeper' weeds that have limited extent at the moment, but whose populations may expand exponentially with the introduction of effective pollinators.


  • Compare foraging profile with native pollinators. On Tasmania it's distributed over a wide range of habitats and uses many different floral resources.
  • Competition for floral resources can be inferred if all nectar is consumed throughout the year, making it a limiting resource.
  • Compare proportion of visits (eg per 1000 flowers) to native versus introduced plants with the proportion of both plants in the system.


  • Examine weeds known to only be pollinated by bumblebees, eg /Lupinus arboreus/, which is only able to be pollinated by powerful bees that can force the flowers apart. It's a serious weed in NZ where bumblebees are present. Introduced to Tasmania but still scarce. Seed set in recently colonised areas has increased dramatically.
  • Look at introductions in other countries - NZ, Israel, Japan, Chile etc.
  • Catch bumblebees and determine origin plants of pollen load
  • Many weed plants are wind or self-pollinated. Exclude bumblebees and other pollinators and see if there are any differences in seed set.


2) Competition for hollows


  • Are all available hollows used? Does removing animals from one cause others to move in?
  • Are the dimensions of hollows used by introduced fauna suitable for the native animals in question anyway?


  • Look. Hollow-bearing trees may be weaker and fall over from year to year. Assess recruitment and loss of hollow-bearing trees over time.
  • Assessing tree growth and decay in general is also informative.
  • As hollows in large trees may be obscured, might require some knowledge of size/age classes, likelihood of hollows. Examining previously felled or fallen trees may be useful.
  • Dimensions (especially internal) are difficult to assess from the ground.


  • If no natural hollows are available, nest boxes might be okay. They are certainly used by some animals.
  • Probably need to install boxes with a range of dimensions, entrances and heights to suit species present.
  • Trees may take dozens to hundreds of years to form hollows.. exact mechanism not well understood. If habitat has been destroyed, could be worthwhile.
  • Probably good because they're not particularly expensive to install and can engage community involvement as well.
  • Reliance on boxes indicates that management is failing to provide sufficient natural hollows and are therefore not ecologically sustainable.