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Yesterday I visited popular theme park Dreamworld at Queensland’s Gold Coast. The visit was to celebrate a 10 year old’s birthday. The highlight for her was the Giant Drop.

We also visited Tiger Island and enjoyed a movie about grizzly and polar bears called ‘The Bears’ shown at the Imax theatre. The photography was spectacular and included grizzly bears catching salmon.

Towards the end of the movie we were told that the survival of polar bears was threatened by global warming. We were told that as a consequence of warmer springs, the ice sheets were thinning earlier than usual at the Arctic and as a consequence the seal hunting season was shorter and bears were losing weight.

Polar bears use sea ice as a platform for hunting ringed seals. Late spring is considered a key hunting period when there are usually lots of fat recently weaned seal pups.

The idea that polar bears are withering away as a consequence of global warming gained prominance following the release of a WWF Report in 2002 titled Polar Bears at Risk. The WWF Report relied on a research paper by Stirling et al titled Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climate change, Artic, Volume 52, Pages 294-306.

This peer reviewed article concludes:

From 1981 through 1998, the condition of adult male and female polar bears has declined significantly in western Hudson Bay, as have natality and the proportion of yearling cubs caught during the open water period that were independent at the time of capture. Over this same period, the breakup of the sea ice on western Hudson Bay has been occurring earlier. There was a significant positive relationship between the time of breakup and the condition of adult females (i.e., the earlier the breakup, the poorer the condition of the bears). The trend toward earlier breakup was also correlated with rising spring air temperatures over the study area from 1950 to 1990. We suggest that the proximate cause of the decline in physical and reproductive parameters of polar bears in western Hudson Bay over the last 19 years has been a trend toward earlier breakup, which has caused the bears to come ashore in progressively poorer condition. The ultimate factor responsible for the earlier breakup in western Hudson Bay appears to be a long-term warming trend in April-June atmospheric temperatures.

While the western Hudson Bay bears appear to be a bit thinner today than they were 20-odd years ago, there has not been a corresponding decline in population numbers. WWF and others acknowledge that the western Hudson Bay population is stable at about 1,200 polar bears.

There are thought to be about 22,000 polar bears worldwide with about 60 percent in Canada. Most bear populations are thought to be stable or increasing in number. Historically hunting has impacted on population numbers and over-harvesting is still considered the main threat to polar bears.

I recently found this site that includes some photographs and a map of the arctic and where to find polar bears,
http://www.polarbearsinternational.org/arctic-map/ .

While it is important to note that western Hudson Bay bears have been losing weight, and that from 1979 to 1998 the trend has been towards an earlier breakup of ice and thus a loss of ‘feeding platforms’ for the resident bears, the evidence is hardly adequate to conclude global warming will result in the extinction of polar bears.

It is interesting to note that the mean time of freeze-up did not change. Furthermore, in eastern Hudson Bay temperatures have been cooling over the same period that they have been warming in the west and the ice has not been breaking up earlier in spring in the east. The total ice cover for Hudson Bay (east and west) did not decline over the study period. Furthermore a distinction should perhaps be made between global warming and climate change?

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.

I spent yesterday in the Northern Territory’s Kakadu National Park. It was a truly magnificent experience.

I was surprised to learn that in the wet season 75 % of the park becomes covered in water much of it runoff from the Arnhem Land escarpment. I was also surprised to learn that about 75 % of the park is burnt each year.

And I was surprised to see cattle grazing in the park, view image (about 70 Kbs).

When I asked a local about this beast I was told “We would prefer they weren’t here, but these cattle are owned by one of the traditional owners and she lets them come out”.

I understand there were once 300,000 buffalo in the area but this number has been reduced to 1,000.

With the reduced number of buffalo, I am told the water is not so muddy and so there are a few more water birds. I saw a tremendous diversity yesterday including sea eagles,view image (about 70 kbs)and magpie geese.

My favourite was perhaps this comb-crested Jacana, view image (about 70kbs) – also know as a Jesus-birds because their 8 cm long toes enable them to almost walk on water.

Interestingly it is the male jacana that looks after the eggs – usually on a lilly pad. When danger threatens Dad has been know to tuck a few eggs under a wing and run somewhere safe. Mum may mate several times during the one season, leaving a few males each with a clutch of eggs to raise.

There were once only about 5,000 crocodiles in the Northern Territory. The population was decimated in the late 1940 and 1950s by hunters. A ban was placed on hunting and the exportation of skins in the early 1970s. Croc numbers have bounced back and are now estimated at 70,000.

I took this photo of a crocs eye today in Darwin –
view image. My image editing software is not on this computer and thus this image is rather large at 450 kbs and might take a little while to download.

Dr Grahame Webb was involved with the program to rebuild croc numbers. He told me the following three principles were promoted:
1. public education;
2. a program to contain problem crocs including trying to keep crocs out of Darwin harbour;
3. ensuring crocs had a commericial value – so landholders saw them as an economic asset rather than a pest.

About 20,000 eggs and 600 crocs are harvested from the wild each year under a permit system. Eggs sell for about $40 each while crocs sell for perhaps $500.

Many locals wish there weren’t so many… so they could swim at the beach again.