Our non-destructive revegetation trial is now under way at Flood Creek. Many thanks are due to the Green Army team that came and helped, consisting of: Alex, Dylan, Tiarnah, Nicole and Chloe. Thanks Guys! The team was provided by Skillset under the auspices of the Federal Government’s Green Army programme and was locally hosted by the Upper Shoalhaven Landcare Council.
We planted a mix of casuarinas and teatree alongside a section of Flood Creek on the Braidwood Common. These were interspersed in some areas with snowgums, yellowbox, blackwood, red-stem wattle and callistemon. All up, around 800 native trees and shrubs went in. Further plantings will follow over time.
For those who are unfamiliar with the concept of non-destructive revegetation, I’ll give a brief outline of the theory. The main point is that we didn’t begin this planting work by destroying any of the existing riparian habitat. Although this section of Flood Creek is currently stabilised by non-natives (mainly willows and hawthorns), we don’t see removing these plants as necessary or desirable in order to increase biodiversity and habitat value.
Several native animal species already utilise the riparian corridor along Flood Creek (including swamp wallaby, wombats and platypus). Destruction of the existing vegetation would obviously cause massive ecological disturbance and probably make this area uninhabitable for decades. Moreover, removal of mature riparian trees accelerates peak flows, increasing the likelihood of downstream flooding and raising the risk of local erosion, as occurs time after time following willow destruction activities–sometimes misnamed “revegetation”. Many Australians are opposed to this form of environmental destruction, but the removal industry remains profitable due to outdated environmental funding programmes.
The non-destructive revegetation activities occurring at Flood Creek will leave the existing riparian habitat in place. This provides a sheltered nursery for new plantings by maintaining the existing windbreak and giving some shade throughout our hot and generally dry summers. Assuming the aim of revegetation is to improve our local environment, we see no advantage in trying to return this creek to a parched and bare ecological ground zero before reintroducing more native plants.
Some environmental history…
Many of the “creeks” across southeast Australia are actually badly incised swampy-meadows or chain-of-ponds systems (Eyles 1977, Prosser 1991, Mactaggart et al. 2006). Early European occupiers witnessed the erosion that cut through these flow-line features following the arrival of hoofed grazing animals and they often planted willow trees to help stabilise valuable and productive farm soils.
Planting willows to prevent erosion was officially supported by various government agencies right through till the mid to late 1990’s. But, around this time, a new fashion came to dominate bureaucracies charged with promoting land conservation: a fashion for puritanical nativism.
The gradual rise of nativism was tied to a radical Australian cultural revision which long sought to overthrow the old-order influence of the British peerage and our perceived ‘cultural cringe’, and to embrace and celebrate all things Australian. The ramifications of this push have been felt across Australian society, in politics, the media, the arts, and in the newly emergent desire for conservation of Australian heritage, including environmental heritage. Willows and all other non-native species were now associated as part of the generalised environmental disturbance caused by Europeans, their agriculture, their mining, urbanisation, etc…
As a result, in the name of environmentalism, another program of riparian deforestation began….
Where they occur, willows (especially Salix fragilis) have been very effective at stabilising actively degrading landscapes throughout south-east Australia, in part, because they re-sprout following grazing damage and are self-propagating. But the fact that they were so widely planted gives an exaggerated impression of their invasiveness. Furthermore, because they are often the only remaining tree in deforested and drained floodplains, people tend to assume that native riparian species must have somehow been displaced by these ‘invading’ willows. But, in fact, across our productive agricultural floodplains, most pre-existing trees were actively cleared by early European pastoralists, and native reeds and other plants were either eaten out by introduced livestock, or died as the fragile soils (held together by plants not adapted to the new hoofed mega-fauna) compacted, incised and then dessicated.
Like earlier colonial programs of land clearing and habitat destruction, modern riparian deforestation is being carried out at a dramatic pace and is helped along by government promotion and funding. Deforestation programs are a lucrative activity for ‘environmental’ contractors who have used chainsaws, heavy machinery and herbicides to complete their work along thousands of kilometres of our fragile flow lines.
In many areas, the trees are simply removed with no thought of replacing them. Grant money generally does not pay for planting labour so, in the absence of volunteers, the trees are simply poisoned, cut down, and burnt, and that’s it. The picture below shows an example of this. Willows removed from the Molonglo River near Queanbeyan have been piled up since 2010 awaiting incineration. Blackberry, liberated from the shade of the destroyed willow canopy, is now rampantly spreading.
Elsewhere, after willows are removed from an incised flow-line, native trees are often planted beside it; usually about 5 to 10m away from the eroded edge. The image below shows an incision near Lucknow, NSW. The line of verdant green regrowth marks where in-stream willows were cut and removed a few years earlier. Running beside the incision are two planted rows of eucalypts. Unfortunately, this activity does nothing to stabilise or reverse historic geomorphological and hydrological dysfunction, furthermore, it involves the complete destruction of the pre-existing riparian corridor.
Many members of the public (and NRM officials who should know better!) think this is what Australian flow-lines are supposed to look like; a neat incision lined with eucalyptus trees and with steep-sided banks that contain the flow of water–just like in England, except with Eucalypts. In reality, prior to the widespread and dramatic erosion associated with European agriculture (and hoofed grazing animals in particular), southeast Australian catchments up to 100km2 contained no channels at all, just grassy braided flow-lines with chains of occasional discontinuous ponds (Prosser et al. 2001). The trees in the picture above are planted within a typical swampy meadow system that would once have been almost permanently saturated and covered in reeds like Typha or Phragmites. These zones were like huge sponges, spreading and holding back floodwaters in high rainfall periods and maintaining catchment soil moistures during periods of drought.
The planting of eucalyptus trees beside the modern-day incision will do nothing to prevent erosion within it. Destruction of the pre-existing willows destroys their stabilising root mats which contain decades worth of trapped sediment and nutrients. These will now break down releasing a flush of organics and sediment into the water. Consequently, all of the stabilisation and channel infilling that has occurred over previous decades is undone. This could only seem like an environmental improvement where nativist genetic ‘purity’ is the primary assessment criteria being applied.
Our non-destructive revegetation trial is intended to demonstrate a logical environmental approach to improving biodiversity and habitat complexity within degraded agricultural and peri-urban riparian landscapes. As already stated, we are planting native species beside the existing incision, exactly as is already fairly-commonly practised. The only difference is that we are not removing the existing non-native habitat beforehand. It’s as simple as that.
This means the site at Flood Creek will not go through a 15-20 year period without vegetative shelter for the existing swamp wallabies, platypus and other native animals. It will not endure a 50-100 year period without tree hollows or natural contributions to in-stream woody debris. Further, it will not be subjected to the elevated erosion risk that has proved disastrous in other “revegetation” projects.
It seems strange that such a benign approach to environmentalism should be subversive, and yet I think it does pose a challenge to existing revegetation programmes and the funding regimes and bodies that support them.
One major philosophical misalignment which these programmes must face up to is that, often, they are not really focussed on reintroducing native species or increasing biodiversity at all. Instead they are primarily guided by the erroneous belief that simply removing non-natives is automatically an environmental benefit. The re-introduction of native vegetation is regularly a poorly implemented afterthought, or is not bothered with at all–as at the Molonglo River, near Queanbeyan (image above).
It is very easy for professional project coordinators to organise contractors with heavy machinery and herbicides, but much harder for them to find or afford labour for replanting and to ensure permanently-ongoing care for the destabilised local ecology that remains once the existing vegetation is destroyed.
Hopefully the desirability of non-destructive approaches to environmental improvement will be obvious to all and we’ll see more examples of this kind of activity in future. Perhaps actual revegetation might become the focus of revegetation projects in southeast Australia again. Thoughtful, non-destructive, tree planting activities would enhance the environment, and we could turn away from currently-well-funded, but counterproductive, tree removal in our ecologically-vital riparian landscapes.
Is this a crazy idea? What are your thoughts?
Eyles, R.J. (1977). Bircham’s Creek: The Transition from a Chain of Ponds to a Gully Australian Geographical Studies, 15 (2), 146-157 : 10.1111/j.1467-8470.1977.tb00094.x
Prosser, I. (1991). A Comparison of Past and Present Episodes of Gully Erosion at Wangrah Creek, Southern Tablelands, New South Wales Australian Geographical Studies, 29 (1), 139-154 DOI: 10.1111/j.1467-8470.1991.tb00711.x
Prosser, I.P., Rutherfurd, I.D., Olley, J.M., Young, W.J., Wallbrink P.J., & Moran C.J. (2001). Large-scale patterns of erosion and sediment transport in river networks, with examples from Australia Marine and Freshwater Research, 52 (1), 81-99 : 10.1071/MF00033
Mactaggart, B, Bauer, J, Goldney, D, & Rawson, A (2006). The restoration and protection of the swampy meadow within an agricultural landscape Australian Farm Business Management Journal, 3 (2), 68-75
Recommended further reading:
Wilson M. 2006, ‘Willows: Weeds of Retention’, in Hazell Peter and Norris Duane (eds), Natural Sequence Farming- Defining the Science and the Practice, Proceedings of the First Natural Sequence Farming Workshop, 31st Oct-1st Nov, Bungendore, NSW, Australia.