Illawarra Woodland and Rainforest Project

The Illawarra Woodland and Rainforest Project

Project Officer – Richard Scarborough

Minnamurra Rainforest
Minnamurra Rainforest

Biodiversity conservation covers three different aspects of our ecological communities. At the regional level, there is the need to conserve the different types of ecological communities. Within each ecological community, there are the different species that characterise them. Then, for each species, there is the genetic diversity represented in the population.

In the Illawarra, pretty much all our ecological communities are listed as Endangered Ecological Communities (EEC’s). These include Illawarra Lowlands Grassy Woodland, Illawarra Subtropical Rainforest, Swamp Sclerophyll Forest and Littoral Rainforest. With the Illawarra Escarpment vegetation the subject of rigid planning controls, this is all the vegetation between the escarpment and the sea.

The history of vegetation clearance has had an impact on all levels of biodiversity. At the most critical level for species’ survival, the major part of their populations, and of consequence, large amounts of their genetic diversity has been lost. This is further compounded by the fact that remnant vegetation has become isolated in the urban/rural matrix.

The growing concern is that further environmental change will be profound. Given that individuals and species are adapted to their environment through the interaction of their genes, and genetic diversity is what natural selection acts on, do our species have the means to cope with the effects of predicted climate change?

It follows that the functional unit for ecological restoration work must be at the level of the species’ population. There can be no recovery of an ecological community without addressing the reproductive processes of species within them, as each species must have a means to recruit new generations into their populations. Otherwise they go extinct.

Sunset over Seven Mile Beach Gerroa

For plants, reproduction may be achieved by outcrossing – the breeding between different individuals that produces genetically variable offspring – or by inbreeding, a self-pollination event. Inbreeding eventually reduces the level of genetic diversity possessed by individuals, as the act of genetic recombination during formation of pollen and egg cells can result in an individual with two copies of the same gene, as opposed to having alternative forms of that gene.

Gene transfer can reasonably be expected to be compromised in isolated remnants for even the regionally common species, particularly for the foothills below 300 metres and the coastal plain to the beachside vegetation. Perhaps the problem is not an issue for the larger area of the Escarpment, or areas like Seven Mile Beach National Park. But we should include these areas too, because we know that the Escarpment was historically cleared to high levels, and therefore the founding populations may have been small for the regeneration that we see in modern times.

Bleeding Heart
Bleeding Heart

To what extent is it valid to mix the gene pools of populations of species by accessing seeds from different provenances? Which species and/or populations should we be especially concerned about? Will we have an effect on genetic adaptation to local habitat, leading to outbreeding depression? (1) Or will we be undertaking the most important aspect of species recovery, by promoting reproduction between genetically distinct individuals?

The issue of genetic diversity in plants that we use in our revegetation projects has become a recent focus for Landcare Illawarra. From early meetings, we have moved on to producing a discussion paper that includes species’ profiles, as well as locations that catch our attention due to their insularity and low population numbers for species. We are interested in gauging the population structure of species in remnant vegetation, and to plan genetic recovery from there.

The Illawarra Woodland and Rainforest project is being managed by Landcare Illawarra

There is the potential for people to be involved in a broader project that will enhance the genetic diversity of individual species. This would take the form of population assessments and new plantings or additions to existing work. We are interested in establishing what will essentially become seed orchards for different species in the future.

Scrub Beefwood
Scrub Beefwood

Richard Scarborough Project Officer for Landcare Illawarra, worked with the late Anders Boefeldt to produce the discussion paper.

If interested in field assessments, planting projects or the discussion paper, contact Richard on 0438 988 387.

(1) Outbreeding depression refers to cases when offspring crosses between individuals from different populations which have lower fitness than progeny from crosses between individuals from the same population.

How you or your Landcare Group can help…

As a first step, a population assessment for species at your site can be conducted by counting the individuals of each species, or species you think may have low populations. Where there are distinct generations, size can be used as an approximation for age class, and field assessments should indicate the numbers in the founding parent population.

As a second step, seed collections can be undertaken for target species ie. those that have low populations or that are at risk of not being able to cross-pollinate. The aim is to capture the genetic diversity of small populations, or even single individuals in extreme cases, and then produce planting stock for seed orchard projects.

Brush Wilga Fruit
Brush Wilga Fruit

We are also looking for planting sites. A space for three trees for a species would help, but we can work up projects of any scale and for any number of species.

The role of the seedbank will be to act as a clearing house to coordinate seed collections by community members propagated by local nurseries as a source of tubestock for planting projects. Landcare Illawarra would like to encourage a wide variety of people to assist in seed collection to increase the seed collecting effort across the region and therefore improve the outcomes for the conservation of genetic diversity.

Discussions with contracting nurseries have been productive and various nurseries now work in partnership with Landcare Illawarra to propagate seed for the project. Seed collection contributions for the seedbank by members of the community will increase the range of species available as well as the level of genetic diversity for each species.

Collected Fruit
Collected Fruit

As an initial seed collection list, we are targeting species with regionally dispersed distributions, where the closest individual of the same species may sometimes be beyond the means of the pollinator or wind to effect interbreeding. Woodland species are also in demand. The following are useful if you can collect them:

  • Kurrajong, Brachychiton populneum
  • White Beech, Gmelina leichhardtii
  • Yellow Ash, Emmenospermum alphitonioides
  • Celerywood, Polyscias elegans
  • Pink Tips, Callistemon salignus
  • Rose Sheoak, Allocasuarina torulosa

There will be many more species to come as we review their populations. We will also indicate specific sites from which we’d like to collect.

For more information about planting design and the genetic diversity project contact Landcare Illawarra Project Officer Richard Scarborough on 0438 988 387 or email richardscarbrough@dodo.com.au

Clean Energy Future Biodiversity fund…