Freelance Science Writer & Editor

The cool shade of trees

An occasional blog about plants, people and landscape.

On banksia woodlands and physics envy

Viki Cramer - Monday, June 26, 2017

[‘Ecosystem’] is not more complex than we think; it is more complex than we can think.” Frank Egler, 1986.

Ecology isn’t rocket science — it’s much harder. Stephen Carpenter, 2002.

In the late ‘80s and early ‘90s, several prominent ecologists grappled with ‘physics envy’. The twentieth century had seen great progress in the fields of physics, chemistry and genetics. Ecology, they feared, just wasn’t keeping up, despite the adoption of the rigorous experimental methods used in these fields.

Some offered somewhat apologetic reasoning for the slow pace: testing hypotheses in ecology took time, replication of existing studies even longer. Things easily achieved in a laboratory or glasshouse, such as randomisation and control, were much more difficult in a forest, a grassland, or on the edges of the sea.

These things are all true. But then, in 1987, James Gleick’s Chaos: Making a New Science was published. The popularity of the book gave a generation of ecologists more than just a common language with which to describe the complexity they knew existed in ecosystems: it shook loose any idea that ecology was some sort of impoverished cousin of physics. It was the language of mathematics, that close sibling of physics, that let ecology really sing its praises as a science.

Ecology is harder than rocket science because ecosystems can be more than just inherently unpredictable (a feature of chaotic systems); they also show other forms of complex dynamics. They are sensitive to initial conditions and subject to random events. There is no balance of nature, no equilibrium to be consistently returned to.

It is when scientists and land managers try to put an ecosystem back together that we discover just how much we are yet to understand, and how much is outside of our control.

Take banksia woodlands, for instance.

Here no more: banksia woodland at the Fiona Stanley Hospital site. Photo: Cristina Ramalho (used with permission).

Banksia woodlands, where a species of Banksia is the dominant tree in the overstorey, occur only in the south-west of Western Australia. The rest of Australia has it’s fair share of banksia species, but nowhere else are they to be found as canopy trees. Banksia woodlands are a prominent vegetation type on the Swan Coastal Plain, particularly on the heavily weathered and essentially infertile Bassendean Sands. The understorey of these communities is particularly rich in species of shrubs, perennial herbs and sedges.

For many residents, it's the distinctive banksia woodlands that give Perth its sense of place. But they are either being slowly diminished by weeds and fire and careless use or obliterated in one fell swoop to make way for new developments. Last year the banksia woodlands on the Swan Coastal Plain were listed as a threatened ecological community under federal environmental legislation.

These woodlands are not a single community: there are many sub-types, depending on the species of Banksia that dominates the canopy and the composition of the understorey. Some sub-types are more threatened than others. Despite their location within and around the suburbs of one of Australia’s largest cities, the sub-types have never been properly mapped. We are not clear about their geography, let alone their ecology.

Several recent developments – most notably the clearing of 25 hectares of banksia woodland for the Fiona Stanley Hospital and 167 hectares for the extension of Jandakot airport – have triggered offset provisions under  federal environmental legislation and several large restoration projects are underway.

Remaking ecosystems is complicated work. Of the 86 species to be restored as part of the Jandakot airport offset, only 24 can be consistently propagated from collected seed. Many other species are expected to germinate from the topsoil taken from the cleared site and spread at the restoration site, but there was not enough topsoil to cover the extent of the offset area. Banksias are serotinous, meaning they hold their seeds in their cones until an environmental trigger like fire stimulates their release. Thus their seeds are not stored in the soil seed bank, and they must be planted by hand. It takes a mix of approaches – topsoil transfer, direct seeding, hand planting – to ensure that the target number of species are given the best chance of becoming established at the site. It's expensive and it takes time.

Then there’s the unpredictability. Despite the same treatments being applied consistently across a restoration site there can be large variation in the number of plants found in each hectare of land. Low rainfall years see many seedlings die. Perth’s winters have been drying for the past four decades and receiving ‘average’ winter rainfall has become a cause for celebration and relief. Difficult questions emerge about where we should collect seed from or whether we should consider using a different mix of species altogether. A remodelling, if you like, rather than a remaking of an ecosystem.

And there’s the real rub: if there’s a reason for ecologists to envy physics it’s not because it’s a more elegant discipline or because it progresses faster. It’s because physics, as a science, doesn’t need to provide evidence for difficult choices that are wrapped up as much in human values as they are in data.

Which species to save? Which to let go? Which ones to move around the landscape, and from where? Who gets to decide?

These insights about banksia woodlands were gleaned from the Banksia Woodland Management Workshop organised by the Department of Parks and Wildlife (WA) and held at the University of Western Australia on 16 June 2017.

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    Science Writer and Editor Perth Australia
    Viki Cramer   PhD BSc
    Freelance science writer specialising in ecology and the environment.
    Ecologist - Science Communicator - Editor
    Perth, Australia
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