Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

Archives for October 21, 2005

Greenland Getting Taller

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We’ve been told that Greenland is thinning at the margins,and the glaciers are retreating, but while all this is happening the icecaps are now apparently thickening. This is according to a new article in Science as reported by ABC Online:

“Greenland’s icecap has thickened slightly in recent years despite wide predictions of a thaw triggered by global warming, a team of scientists says.

The 3,000-metre thick icecap is a key concern in debates about climate change because a total melt would raise world sea levels by about seven metres.

Satellite measurements showed that more snow was falling and thickening the icecap, especially at high altitudes, according to the report in the journal Science.

Glaciers at sea level have been retreating fast because of a warming climate, making many other scientists believe the entire icecap was thinning.

“The overall ice thickness changes are … approximately plus 5 cms a year or 54 cms over 11 years,” according to the experts at Norwegian, Russian and US institutes led by Ola Johannessen at the Mohn Sverdrup centre for Global Ocean Studies and Operational Oceanography in Norway.

However, they said that the thickening seemed consistent with theories of global warming, blamed by most experts on a build-up of heat-trapping gases from burning fossil fuels in power plants, factories and cars.

Warmer air, even if it is still below freezing, can carry more moisture.

That extra moisture falls as snow below 0 degrees Celsius.”

And some Australian climatologists have said that as it gets warmer it might get wetter. Is it still raining in Perth?

Cattle Killing the Macquarie Marshes?

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I started the week exploring the wetlands of Kakadu National Park in Northern Australia. I have ended the week exploring the wetlands of Central New South Wales (South Eastern Australia) with my friend Gill Hogendyk.

Gill, a trained vet, has always had a particular interest in bird watching. After moving to Warren (just north of Dubbo and south of the Macquarie Marshes) in 1990, Gill started taking a particular interest the birds of the Ramsar listed Macquarie Marshes.

Gill is increasingly concerned that the almost exclusive focus on environmental flows and water use by irrigators (her partner grows cotton) has distracted attention from the potential impacts of grazing on wetland environments including in the Macquarie Marshes.

This aerial photo taken earlier this year of the Marshes, shows the dramatic impact of grazing. The fence is the line of demarcation between an overgrazed private property and ungrazed nature reserve. The impact of grazing here is obvious and dramatic.

Over recent years there has been a focus on Australia’s intensive agricultural industries (eg. horticulture, cotton, sugar) and their environmental impacts with most of these industries undertaking environmental audits and developing codes of practice to address issues of community concern.

The grazing industry has had to contend with bans on tree clearing and been excluded from areas including the High Country, but there seems to have been limited interest in promoting best practice and addressing issues of overgrazing.

In the 1940s and 1950s there were restrictions on grazing and burning in the Macquarie Marshes including:

1. Reeds shall not be burned except with the written consent of the district surveyor,
2. Stock shall be excluded from all (reed) regrowth until 3 foot high, and
3. Rookeries (for bird nesting and breeding) will be completely enclosed with a sheep and cattle proof fence.

I understand that there are currently no such conditions on grazing in the Marshes.

It seems incredible that the flood-plain graziers of New South Wales are screaming so loudly for more water and attracting considerable media attention and yet the issue of overgrazing is being ignored by all.

Aerial photograph showing impact of grazing on the Macquarie Marshes.

The website mantained by the local Marsh management committee explains that The Macquarie Marshes is a large non terminal wetland in central west New South Wales and covers approximately 200,000 hectares, 88 percent of which is privately owned. The Macquarie Marshes Nature Reserve makes up the remaining 12 percent and is managed by the NSW National Parks and Wildlife Service.

UPDATE 24TH OCTOBER 2005

I have received some offline emails assuming that the main problem for the marshes is low flow because of Cubbie Station. The Macquarie Marshes are NOT downstream of Cubbie and the Condamine Balonne system.

Rather as detailed here: The Macquarie River is formed by the joining of the Fish and Campbell rivers near Bathurst. The Turon, Cudgegong, Bell, Little and Talbragar rivers join the Macquarie River as it travels north-west. Near the township of Warren, the Macquarie becomes a complex system of effluent creeks, wetlands and floodplains connecting the Macquarie, Barwon and Bogan rivers. The Macquarie Marshes are the wetland and marsh country of this area, consisting of about 40,000 ha of core wetland with up to 220,000 ha inundated during major floods.

The climate of the lower Macquarie River catchment is semi-arid. Rainfall and altitude decrease from east to west, while temperature increases. The marshes are less than 200 metres above sea level and receive approximately 400 mm of rain per year, although flooding occurs in most years due to rainfall in the headwaters of the catchment and occasionally locally (for example, as happened in 1983 and 1995).

Two sections of the marshes are separated by an isthmus and lie on early Tertiary alluvium. The southern section consists of open water linked by anabranches of the river, and contains reed swamps and other emergent vegetation. The northern marshes consist of more prominent braided channels and more extensive reed swamp and river red gum woodland.