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The natural world. Looking pretty for 3.5b years.

The Colours of Australia are Fading

The Colours of Australia are Fading

Author: Hugh Bollinger/Friday, June 2, 2017/Categories: natural history, wildlife conservation, marine life, sustainability, environment, climate change, Archive Pick of the Week

       Western Australia Kelp Forest, 2011 (credit: University of Western Australia/Thomas Wernberg)

Australia is a very colorful place with its birds, unique plants, lush forests and marine life, as well as the landscape itself. Sadly, some of those brilliant Aussie colors have faded.

Well removed from most people's attention some major deforestation is happening there. This wholesale vegetation loss isn't the type seen in the Amazon Basin or the rainforests of Borneo but to forests in and near the seas surrounding the massive island continent. The consequences will be far-reaching if ecological boundaries are permanently crossed.

Reporting in Science Magazine, a dramatic climate-driven shift has been observed in a marine ecosystem, the Great Southern Reef, that stretches from Tasmania to the coastlines north of Perth on the Indian Ocean. The reef's defining kelp forests have died and being replaced by seaweed turfs. Field research in Western Australia shows that significant warming of the temperate kelp forests there has resulted not only in their collapse, but also in a shift in the kelp community composition. In a very short time span, the kelp died and was replaced by other species preventing reestablishment.

The researchers demonstated in their new article that:

"after decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw the kelp species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of the kelp forests.

Thomas Wernberg, lead author from the University of Western Australia, noted:

Temperatures exceeded anything previously experienced by these forests and they collapsed, allowing algae, tropical and subtropical fish, seaweed, and coral to increase rapidly. We analysed kelp forest data collected between 2001 and 2015 along more than 1200 miles of the Western Australian coastline and it shows how the heatwave, combined with decades of ocean warming, has broken down biogeographic boundaries with lasting consequences.

These productive, biologically diverse, kelp-dominated ecosytems have been replaced by new and lesser productive species. The situation is explained here:

Similarly, another coastal Australian forest has been observed to have undergone major alterations recently. Mangrove forests fringe many shorelines extending well into tidal zones where they serve as critical nurseries for species, are used for recreational and commercial fishing, and represent protective barriers against cyclones that hit Australia's coasts frequently.

News reports show that nearly 10,000 hectares (~25,000 acres) of mangroves have died across a wide stretch of coastline reaching from Queensland to the Northern Territories, of the 'Top End'. The dieback occurred again in an extremely short period of one month coincident with the bleaching of corals on the Great Barrier Reef in response to stresses from el nino and higher ocean temperatures. Some of the damage to these mangrove forests is in such remote locations, even for a continent the size of Austalia, that data and photography to determine the extent of the dying had to be obtained from satellites.

Quoted by the ABC, researcher Norm Duke from James Cook University in Queensland said:

"no doubt the mangrove dieback was related to climate change and it is world-first in terms of the scale of mangroves that have died."

            

                       Dying Mangrove Forests, Queensland, Australia, 2016 (photo: Norm Duke, JCU)

The diversity of an ecosystem is often celebrated as a strength and a sign of resilience. However, this diversity can be dramatically affected if that diversity itself is dependent on one or a limited number of key elements in the ecology: a dominant growth-form (kelp or mangrove forests), a dominant physical structure (coral reefs), or a stable coastal temperature (marine tidal zones).

Along with the loss of marine forests, the diversity of colors associated with all the dependent species has been lost as well. The songwriter Enda Kenny has written a soulful tune of his own artistic impressions about the Colours of Australia fading:

The ecosystem collapse recently experienced in Australia is impressive, very sad, and should be of concern to more than just the Australians.

WHB

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