Today is National Tree Day. The day we are meant to plant trees. Two days ago New Scientist published an article titled ‘Planting trees may create deserts’. It went on,
Planting trees can create deserts, lower water tables and drain rivers, rather than filling them, claims a new report supported by the UK government.
Indeed studies in WA have indicated that clearing regrowth in the Perth catchment could increase runoff to dams by 40 gigalitres. This would almost replace the need for the desalination plant?
According to ABC Online,
More than 300,000 green thumbs will descend on sites around the country today to participate in National Tree Day.
Organisers say they have been heartened by an increase of almost one-third in the number of volunteers planting trees and shrubs to restore biodiversity.
Yeah. There are some places that will really benefit from more trees. But let’s also recognise that too many trees can destroy biodiversity.
Michael Duffy makes some reference to this in his piece in yesterday’s SMH titled ‘Carr’s green legacy is a black mark’:
Creating a national park and then, as this Government has done, largely letting “nature take its course”, means this history stops. Gradually the vegetation thickens, the fuel load grows, the animal populations expand, and weeds proliferate. The park becomes a sort of toxic ecological volcano, spewing out fire, kangaroos, weed seeds, and feral animals such as wild dogs into the surrounding countryside. It takes a few decades to reach this point. A lot of our national parks were created in the 1970s and 1980s, which is why these problems started to become acute in the 1990s.
We can expect these problems to occur at Yanga, where (according to the station’s website) the environment of two endangered species – the Australian bittern and the southern bell frog – depends on keeping the red-gum forests open by logging, which will now cease.
Thanks to J.F. Beck at http://rwdb.blogspot.com/2005/07/killer-trees.html for alerting me to the piece in New Scientist.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Oh yes – Australia’s national parks are dreadful places. Totally unpopular. Nobody ever visits them as they are so bad. The closer they are to cities – the worse they are too …
When I was at Lamington last Xmas – I arrived at a deserted car park with burnt out stolen vehicles – no people. The Park – well it was overgrown with weeds and a source of wild dogs that were eating Gold Coast children. I was shocked… If only they’d give the place a good bull-dozing and burning it would help it no end…
Yes I can well imagine trees destroying “biodiversity” – it’s usually when they’re replacing an already stuffed system with trees. See Fraser Island revegetation – might be a Tristania forest – and that’s about it for species – one. But it looks green from the road.
See Mulga forests in Queensland are a result of overgrazing and lack of fire.
And how thoughtful of the aborigines to log the red-gum forests before we got here. Probably explains their nice little huts and shiny saws that the early explorers remarked on.
There are aspects of Australia’s National Parks that ARE dreadful and at the same time there are aspects that are undisputably valuable.
The statutory provision of sanctuary for feral animals and weeds that destroy the ecological processes that are reserved for protection is dreadful.
The political and bureaucratic investment in a public perception that Australia’s biological diversity and ecological integrity are protected through the declaration of reserves that have no capacity to provide protection against disrepectful environmental impacts (feral animals, weeds, fires, vandalism, official ineptitude/inaction) is also dreadful.
So is the cultivation of a public perception that the provision and management of National Parks for recreational enjoyment is without cost, that the commercial gain from tourism operations costs only $1.20 per person and that the millions of dollars of subsidisation for maintaining these illusions has no economic impact on conservation off-reserve.
It is dreadful that remote communities are robbed of salaries under the environmental pretence of protection through the declaration of another National Park under the administration of already over-burdened and under-resourced bureaucracies.
I’ll have to think a little longer about those aspects that are undisputably valuable.
The current issue of The Economist notes that the study you refer to – a four-year British-Dutch study published by Britain’s Department for International Development – identifies several myths about the link between forests and water. For example, in arid and semi-arid areas, trees consume far more water than they trap.
In South Africa trees lose water through evaporation at twice the rate of grassland or South Africa’s unique fynbos scrubland. The SA government now penalises forestry companies for preventing this water reaching rivers and underground aquifers.
In India, large tree-planting schemes not only lose valuable water but distract attention from the major problem: the unregulated removal of water from aquifers to irrigate crops.
The report concludes that there is no scientific evidence that forests increase or stabilise water flow in arid or semi-arid areas. It recommends that, if water shortages are a problem, governments should impose limits on forest plantation.
The Economist also notes research into the carbon cycle in the forests of the Amazon basin in a paper published in Nature. A team of American and Brazilian scientists found that trees were silently returning the carbon after just five years.
As you have noted before, facts are essential for sensible environmental policy.
in our area tree planting lowers our salty water table – great ! grasses and small wattles grow easily as understory .however high planting density in a low rainfall area is unrealistic.
“yanga station” if managed properly should be a gem in southern australia . congratulations to the Black family and the nsw government for giving it to all australians. however light grazing and or fire, will be essential to maintain its biodiversity .
A late comment on terminology.
Studies in WA are merely a reflection of a commonly observed response of stream flow to thinning of regrowth forests. This is not clearing – clearing is something agriculture does to forests (so that I am able eat). Thinning is significantly different; it is a mimic of the normal processes of forest maturation. If you want more water and more productive forests, you can have your cake and eat it too.
The UK report merely illustrates that if you take an environment that is in equilibrium and disturb it, there are often unforeseen environmental consequences as the landscape seeks a new equilibrium. The perceived original equilibrium may be either a “natural” or pre-human-influence condition, or it could be the result a severe human impact made so long ago that the original human-induced change has been forgotten. For an example of the latter, see Europe. When Europeans dispense gratuitous advice to other nations about environmental managment, they often forget that they have obliterated the natural environments in their own nations. They are managing their highly modified and simplified environment quite well in many respects, but it’s best to get all your deforestation and mass extinctions out of the way before anyone else notices.
In some parts of Australia, the European culture of total fire suppression and the armchair conservationist enthusiasm for National Parks means the normal control of tree regeneration provided by frequent fire in natural grasslands is halted, there is increased tree cover and then reduced stream flow. Conversely, in another region, removal of a pre-European forest, woodland or heath scrub for agriculture may cause increased streamflow and mobilisation of normally stable soil salts. So the centralist approach of uniform national responses to environmental problems is often too simplistic.
There are no general rules for all situations, other than, if you disturb it, then you have to manage it from there on. The creation of National Parks for electoral success in the capital cities is truly short-sighted. The NPs are often effectively a “no-management” policy applied to an already disturbed environment, so these Parks will become an increasing burden upon the state and the Parks’ neighbours as the Parks trend towards some new, perhaps unexpected, state of equilibrium. It is possible that this trend may be via a period of collapse.
I’ve just revisited the Blue Mountains, a favourite holiday destination, where the effects of the fires about two years ago are plain to see and very disturbing. We were last there a few months after the fires and I thought we would see evidence of better recovery on the most recent visit. Unfortunately the extent of tree deaths has become more apparent, not less. It is appalling what a fire-exclusion policy has done to the structure and species composition of those (previously) beautiful forests. And that’s in the NP on Sydney’s doorstep, so I am not surprised there is some concern about the many new Parks that are remote from George Street. Bob Carr knows when to bow out – before too much poultry comes home to roost.