Saving the world’s ecosystems one A at a time

By Tim ConnellMarch 15th, 2021

Scientists examine 19 ecosystems under pressure, from the beautiful to the rare.
Lush green forest and mountains surrounding a lake at Cradle Mountain, Tasmania

Healthy subalpine forest at Cradle Mountain, Tasmania. Image by Daniel Engelbrekt/Pixabay

The warnings of climate change have developed a language of their own; clear and present calamities are framed as canaries in the mineshaft and tipping points.

But a landmark paper has found that if things continue as they are in much of Australia, this familiar narrative will intensify. The 38 scientists who co-authored the study, published in Global Change Biology, foreshadow ecological collapse from the tropics to Antarctica. They also offer a plan to tilt that trajectory.

The paper’s authors examined 19 ecosystems spanning 7.7 million square kilometres, about 1.5 per cent of the surface of the Earth. They sweep from northern Australia to coastal Antarctica, covering desert, mountains and rainforest, marine and freshwater ecosystems.

A new approach helps prevent ecosystem collapse

A new approach dubbed the Three As – Awareness of the importance of ecosystems, Anticipation of risks and rapid Action – defines the approach for CSIRO transdisciplinary researcher and study co-author Dr Jess Melbourne-Thomas.

“Awareness and Anticipation are ways that we can seek to minimise or prevent ongoing damage, change and collapse for ecosystems into the future. In terms of impacts that have already occurred there are Actions that can be taken to lessen these impacts and assist recovery,” Dr Melbourne-Thomas, based at CSIRO Oceans and Atmosphere in Hobart, says.

“Where the environment is so changed that natural recovery isn’t possible, we may need to adapt by changing some elements of a system, for example by creating new habitat or actively moving species.”

The study considers each biome over the last two centuries, and how it has changed in 30 years. It outlines how each ecosystem has transformed, to what degree, and its chances of recovering.

The drivers of collapse (defined as potentially irreversible change to ecosystem structure, composition and function) are characterised by their scale and origin. This means considering the impacts of global climate change, as well as each place’s regional human impacts. The study identifies longterm “presses”, such as climate trends, habitat loss, invasive species and pollution, and acute effects or “pulses”, including storms, heatwaves and wildfires.

The pathogen-affected Macquarie cushion plant looking brown and dead on Macquarie Island, halfway between New Zealand and Antarctica. Image by Cath Dickson

The pathogen-affected Macquarie cushion plant on Macquarie Island, halfway between New Zealand and Antarctica. Image by Cath Dickson

Climate Change stresses and impacts can be severe

The ominous message is that for every familiar plight like that of the Great Barrier Reef, there are other ecologies fading out of sight and out of mind.

For example, in the summer heatwave of 2010-11, Western Australia’s world heritage-listed Shark Bay lost a third of its seagrass meadows. The seagrass is among the most abundant and diverse in the world, and supports a complex food-web helmed by tiger sharks, manta rays and the dolphins. The area protects about a tenth of the world’s dugongs, which only eat seagrass. About 350 kilometres north at Ningaloo Reef, known for whale sharks, climate change “pulses” include rapid rises in sea surface temperature and cyclonic weather.

The pressures have grown more severe, widespread and frequent. Nine ecosystems recently absorbed their most extreme presses or pulses on record, by severity or spatial scale. The 2019-20 marine heatwave on Australia’s west coast accompanied an unprecedented, continent-wide land heatwave. December 18, 2019, was the hottest recorded Australian day, at an average 41.88° C.

The heat prompted the highest average Forest Fire Danger Index on record. Severe drought exacerbated the conditions, leading to fires across an unprecedented 18.6 million hectares, mainly in eastern temperate forests. The Gospers Mountain fire, Australia’s largest recorded single forest fire, burned 81 per cent of the Blue Mountains World Heritage Area.

The Black Summer scorched and choked Australian tropical savanna, Murray-Darling Basin waterways, Montane and subalpine forests, Mediterranean forests and woodlands, Snow patch herbfields and Mountain ash forest ecosystems. Even apart from the estimated three billion animals killed that summer, Australia’s fauna is vanishing from many of the 19 studied biomes. In December 2018 about 23,000 spectacled flying foxes, a third of the national population, died from the heat outside of Cairns, Far North Queensland. A fortnight later, more than a million fish also died in the drought-hit Darling River near Menindee in outback NSW. Such scenes would be biblical, if they weren’t explained by presses, pulses and science.

Picture of healthy yellow kelp growing under water in Eastern Tasmania.

Healthy kelp off eastern Tasmania. Image by Olivia Johnson

Recognising the beauty and value in nature

Dr Justine Shaw is a conservation ecologist with the University of Queensland, and a co-author and instigator of the collaborative study. She is also a frequent visitor to Macquarie Island, halfway between New Zealand and Antarctica. It is a place where few go, a place that is heard and smelled before it emerges from the mist, a 35-by-five kilometre green island heaving with penguins and seals. It is also home to every Macquarie cushion plant on Earth.

Even here, life is collapsing. The cushion plant has gone from healthy to critically endangered in three years. Thirty per cent of it is gone. The endemic cushions, some centuries old, are dying because of windier, drier conditions.

“If we can’t protect our world heritage wilderness areas, if we’re seeing impact in Antarctica, we’re kind of in dire straits,” Dr Shaw says.

“Because they’re really simple ecosystems; the cushion plant is the keystone of this sub-Antarctic tundra. It’s really easy to see what happens when you lose that species from that ecosystem without other confounding effects. There is no bushfire or agriculture or pollution, so we can clearly determine how species interact and it’s very clear what happens when they start to decline.”

People are acting now

If the scenarios are bleak, the study cites successful responses to recent disasters. In early 2016, dry lightning strikes in hot conditions ignited pockets of Tasmania’s ancient Gondwanan ecosystems. Five years on, the Tasmanian government has installed sprinklers and retardants in the forests themselves.

“We need people to be able to understand and acknowledge the value of these ecosystems. Often we don’t realise that until it’s gone. We do understand the value of the seagrass, the kelp forests,” Dr Shaw says.

“And we need to anticipate the threats that are coming.”

1 comments

  1. Ecosystem collapse can occur overnight. We lost the wingecarribee swamp, with two endangered plants and a rare insect, the giant dragonfly, overnight in a heavy rain/flood. Of course, the peat mining that had gone on for some years had a bit to do with it

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