Our EcoCheck series takes the pulse of some of Australia’s best-known ecosystems to find out if they’re in good health or on the wane.
When the first European settlers travelled into the jarrah forests of Australia’s Southwest, they found a vast area of giant trees and imagined an inexhaustible forest. The timber industry took off. Within 100 years, Western Australia’s Conservator of Forests, Charles Lane Poole, noted that: “Sentiment may dictate the preservation of a few … as reminders … but whole forests of giant trees will no longer be seen.” How right this early conservation visionary proved to be.
Today only 5% of the Jarrah forest is in protected areas such as nature reserves or national parks. Although more than 45% is still natural vegetation (much due to Lane Poole’s efforts), virtually none of the forest has escaped some degree of logging, and there are now few signs of the once iconic giant jarrahs. The timber industry and other disturbances have transformed the structure of the forest – what mostly remains now is low-growing jarrah saplings and woodland trees.
What’s more, Australia’s Southwest has been in the grip of human-triggered climate change since around 1970. Along with other Mediterranean-type climate regions, this area is rapidly drying due to global warming, with rainfall declines of 15-20%. This drying trend poses a major new threat to conservationists and industry in aiming to restore these unique forests.
What is to become of them, and what should we do about it? Under the present climatic regime, the jarrah forest is unlikely ever to return to the stature seen by early colonists. We can safeguard what remains, while acknowledging profound loss in many areas.
Jarrah (Eucalyptus marginata) naturally grows in low-fertility, gravelly soils in a highly seasonal Mediterranean-type climate. Depending on the conditions, it can grow into a shrub or a mighty tree, although in areas of low fertility, giant trees require access to a water table.
The declining rainfall, particularly in autumn and early winter, has shifted the region’s creeks and streams from year-round to seasonal, and caused water tables to decline. There have been observed declines in groundwater in some catchments of half a metre per year since 1995, and the problem is forecast to get worse still over the coming decades.
So far, the result has been that most forest cover has been lost in lower-rainfall, inland margins, as well as in more intensively logged, high-rainfall zones. In 2010, an extremely dry year even by today’s standards, even typically high-rainfall zones lost forest cover in areas where soils were shallow and couldn’t retain as much water.
As these changes continue, the jarrah forest will become structurally unrecognisable. Many stands of trees will die, with jarrah persisting as a shrub or woodland tree. However, the understorey will remain incredibly diverse.
The dead and reduced trees will leave a great deal of dead wood around. Undoubtedly there will be a threat of increased bushfires to contend with.
Fire is a naturally frequent (and evolutionarily important) aspect of the Southwest’s Mediterranean climate. But a warmer, drier climate with more extremes of fire weather will make bushfires more frequent and severe, as forest fuels dry more readily and burn for longer once ignited.
More intense bushfires will put extra stress on forest ecosystems, meaning that they take longer to recover. Habitats such as wetlands and rock outcrops, which in the past have provided refuges from fire, will be less able to do so.
Thinning of the forest has been used as a management tool to increase yield into water supply dams. This approach also has potential to more rapidly restore pre-logging or pre-fire forest structure. However, recent thinning in the jarrah forest has failed to increase stream-flow.
Thinning is increasingly ineffective. This is because in a drying climate, it would first need to reverse decline in groundwater levels. Such treatment is not now likely to be achievable without a return to a pre-1970 rainfall regime.
The area has also been previously mined for bauxite (aluminium ore), and the rehabilitation of these mine sites will need to be done in a way that recognises the new, drier water regime. Restoring these areas with trees to provide future sawlogs would have been appropriate in a stable, high-rainfall climate, but not today.
Broader forest thinning is expensive and would probably result in the loss of forest carbon. But more targeted thinning, perhaps by culling invasive plants from the forest, could still be useful for increasing water flows. Leaving the remains of the culled plants on-site would also limit carbon emissions.
Together, unsustainable logging and the shifting climate has lowered the biomass and changed the structure of the jarrah forest. The only form of timber industry with any future in this environment is the collection of coarse woody debris. But this material is worth so much more to the environment and so much less to industry that it’s questionable whether it can be justified at all.
A few remaining venerable “king jarrahs”, and elements of old-growth characteristics, are all that remain of the original forests. But the rest of the mighty jarrahs are gone, and so the focus needs to shift to the importance of this area for the great biological diversity that does remain.
We need a new, wider vision for the vegetation of the jarrah forest. It now needs to be valued as a biologically diverse environment harbouring venerable trees from a former era.
Retention as public land allows maintenance of important conservation values. Thus, best practice rehabilitation focused on the understorey, should now target a resilient jarrah forest under changing environmental conditions. Prudence would reestablish understorey in future rehabilitation and reassess previous rehabilitation. Restoration of surrounding degraded forest may also be possible. These approaches may provide a future for this ecosystem, despite inevitable change.
Meanwhile, the increasingly scarce giant jarrahs that remain are the living museums of the forest – our irreplaceable Notre Dames.
Are you a researcher who studies an iconic Australian ecosystem and would like to give it an EcoCheck? Get in touch.
Antarctica is already feeling the heat of climate change, with rapid melting and retreat of glaciers over recent decades.
A recent article on The Conversation raised the concept of “climate tipping points”: thresholds in the climate system that, once breached, lead to substantial and irreversible change.
Such a climate tipping point may occur as a result of the increasingly rapid decline of the Antarctic ice sheets, leading to a rapid rise in sea levels. But what is this threshold? And when will we reach it?
The Antarctic ice sheet is a large mass of ice, up to 4 km thick in some places, and is grounded on bedrock. Ice generally flows from the interior of the continent towards the margins, speeding up as it goes.
Where the ice sheet meets the ocean, large sections of connected ice – ice shelves – begin to float. These eventually melt from the base or calve off as icebergs. The whole sheet is replenished by accumulating snowfall.
Floating ice shelves act like a cork in a wine bottle, slowing down the ice sheet as it flows towards the oceans. If ice shelves are removed from the system, the ice sheet will rapidly accelerate towards the ocean, bringing about further ice mass loss.
A tipping point occurs if too much of the ice shelf is lost. In some glaciers, this may spark irreversible retreat.
One way to identify a tipping point involves figuring out how much shelf ice Antarctica can lose, and from where, without changing the overall ice flow substantially.
A recent study found that 13.4% of Antarctic shelf ice – distributed regionally across the continent – does not play an active role in ice flow. But if this “safety band” were removed, it would result in significant acceleration of the ice sheet.
Antarctic ice shelves have been thinning at an overall rate of about 300 cubic km per year between 2003 and 2012 and are projected to thin even further over the 21st century. This thinning will move Antarctic ice shelves towards a tipping point, where irreversible collapse of the ice shelf and increase in sea levels may follow.
Some areas of West Antarctica may be already close to the tipping point. For example, ice shelves along the coast of the Amundsen and Bellingshausen Seas are the most rapidly thinning and have the smallest “safety bands” of all Antarctic ice shelves.
To predict when the “safety band” of ice might be lost, we need to project changes into the future. This requires better understanding of processes that remove ice from the ice sheet, such as melting at the base of ice shelves and iceberg calving.
Melting beneath ice shelves is the main source of Antarctic ice loss. It is driven by contact between warmer sea waters and the underside of ice shelves.
To figure out how much ice will be lost in the future requires knowledge of how quickly the oceans are warming, where these warmer waters will flow, and the role of the atmosphere in modulating these interactions. That’s a complex task that requires computer modelling.
Predicting how quickly ice shelves break up and form icebergs is less well understood and is currently one of the biggest uncertainties in future Antarctic mass loss. Much of the ice lost when icebergs calve occurs in the sporadic release of extremely large icebergs, which can be tens or even hundreds of kilometres across.
It is difficult to predict precisely when and how often large icebergs will break off. Models that can reproduce this behaviour are still being developed.
Scientists are actively researching these areas by developing models of ice sheets and oceans, as well as studying the processes that drive mass loss from Antarctica. These investigations need to combine long-term observations with models: model simulations can then be evaluated and improved, making the science stronger.
The link between ice sheets, oceans, sea ice and atmosphere is one of the least understood, but most important factors in Antarctica’s tipping point. Understanding it better will help us project how much sea levels will rise, and ultimately how we can adapt.
Felicity Graham, Ice Sheet Modeller, Antarctic Gateway Partnership, University of Tasmania; David Gwyther, Antarctic Coastal Ocean Modeller, University of Tasmania; Lenneke Jong, Cryosphere System Modeller, Antarctic Gateway Partnership & Antarctic Climate and Ecosystems CRC, University of Tasmania, and Sue Cook, Ice Shelf Glaciologist, Antarctic Climate and Ecosystems CRC, University of Tasmania
As the summer ends, heat is dominating the meteorological landscape, with the warmest month ever recorded and the drought continuing unabated in California. At the same time, it is clear that an El Niño is building that is expected to culminate in the fall and last until the winter, with the possibility of it becoming a “mega” El Niño.
The hope in California is that the large amounts of precipitation usually associated with extreme El Niño events would lessen the impacts of the state’s multi-year drought by partly refilling reservoirs and groundwater, even as scientists caution that this might not happen to the degree needed to alter the present situation.
What drives the El Niño weather pattern and what do scientists know about El Niño under man-made greenhouse warming?
To be clear, El Niño is a tropical Pacific phenomenon, even though it represents the strongest year-to-year meteorological fluctuation on the planet and disrupts the circulation of the global atmosphere. When sea surface temperature changes – or anomalies – in the eastern equatorial Pacific exceed a certain threshold, it becomes an El Niño.
What are the mechanisms behind El Niño? In normal conditions in the tropical Pacific, the trade winds blow from east to west, driving ocean currents westwards underneath. These currents transport warm water that is heated by low-latitude solar radiation and eventually piles up in the western Pacific. As a result, heat accumulates in the upper ocean.
The warm water evaporates from the ocean surface, and the light, warm and humid air rises, leading to deep convection in the form of towering cumulonimbus clouds and heavy precipitation. As this air ascends, it reaches upper levels of the troposphere and returns eastwards to eventually sink over the cooler water of the eastern Pacific. This east-west (zonal) circulation is called the Walker Circulation.
This circulation gets disrupted every few years by El Niño or enhanced by La Niña, the opposite effect. This periodic, naturally occurring phenomenon is called the El-Niño Southern Oscillation (ENSO).
During the typical El Niño, the warm phase of that oscillation, the trade winds weaken, and episodic westerly wind bursts in the western equatorial Pacific generate internal waves into the ocean. These waves trigger the transport of the warm water from the west to the east of the basin.
This induces a reduction of the upwelling (upward motion) of cold water in the east, at the equator and along the coast. It also creates warm sea surface temperature anomalies along the equator from the international dateline in the Pacific to the coast of South America.
As the central part of the Pacific warms up during El Niño, the atmospheric convection that normally occurs over the western warm pool migrates to the central Pacific. That transfer of heat from the ocean to the atmosphere gives rise to extraordinary rainfall in the normally dry eastern equatorial Pacific. Warm air then flows from the west, feeding this convection and further weakening the east-west-flowing trade winds. This leads to further warming as this feedback loop amplifies the phenomenon and ensures that deep atmospheric convection and rainfall patterns are maintained in the central equatorial Pacific. El Niño eventually ends when changes in the ocean cause negative feedbacks that reverse the dynamics that create the El Niño effects.
In association with El Niño, the heat redistribution in the ocean creates a major reorganization of atmospheric convection, severely disrupting global weather patterns from Australia to India and from South Africa to Brazil.
What explains the specific effect on the US and California, however, is a particular type of connection – called extratropical teleconnections – between the heating generated by El Niño and North America. This heating excites wave trains, or groups of similar-sized atmospheric waves, that propagate northward, connecting the central equatorial Pacific to North America. This shifts the subtropical jet stream northward and induces a series of storms over California and the southern US, in general. The increased precipitation that ensues seems to only occur during a strong El Niño.
While El Niños have a rather “typical” signature in the tropics, their impacts over North America vary because other influences act in temperate climates. Nevertheless, most El Niño winters are mild over western Canada and parts of the northern central United States, and wet with anomalous precipitation over the southern United States from Texas to Florida.
Scientists are now studying the diversity in El Niño behavior – strong and weak ones, changes in duration, and the different regions for the maximum SST anomalies. Are these changes to El Niño related to global warming? It is too early to say.
For one thing, there is significant natural variability in the Pacific over the decade-length and longer time scales, which could be masking changes driven by global warming.
Climate models do suggest that the mean conditions in the Pacific will evolve toward a warmer state. That means sea surface temperatures are likely to rise and the trade wind to weaken, which could lead to a more permanent El Niño state and/or more intense El Niño events.
Some climate model projections, together with reconstructions of past El Niños, provide empirical support for more extreme El Niño events under greenhouse warming. They also point toward an eastward shift of the center point where heat from the ocean transfers to the air. This would mean an eastward shift of extratropical rainfall teleconnections, the phenomenon responsible for weather changes in North America, including more rain in the West.
But models diverge in their predictions of whether and how the teleconnections’ intensity will change. So there is no simple answer to how precipitation will change in California in association with changes of El Niño related to greenhouse warming.
Will the sensitivity of the atmosphere to the primary mechanism at the heart of El Niño – that is, feedback between the higher sea temperatures and slowing trade winds, leading to atmospheric convection over the central Pacific – continue in the future?
It was not maintained during 2014, when otherwise favorable conditions for a big El Niño were present. In that case, persistent deep convection did not occur in the central Pacific, and the usual strong interaction between the atmosphere and the ocean there failed to play its normal role in anchoring the convection and heat transfer.
These results show us that we still have much to learn. This is true despite the dramatic scientific progress that has been accomplished over the last few decades regarding El Niño and ENSO cycles, including new theories, sophisticated seasonal forecasting models and extensive observation systems.
Our ability to predict El Niño and the potential connections between increasing greenhouse gases and El Niño is still limited by the complexity of the ENSO dynamics, as exemplified by the failed prediction of a 2014 El Niño. In the meantime, we can look forward to a winter when El Niño, perhaps even a mega El Niño, will dominate the weather discussion.
Australia has one of the worst extinction records in the modern world. Since European settlement, a third of the country’s native mammals have disappeared. How can we stem the losses?
A recent article in Nature highlighted that most federal and state biodiversity conservation policy fails to recognise biodiversity as a major source of industrial products.
Much as explorers chart new territories, chemists, materials scientists, engineers and biologists are exploring biodiversity for medicine, agricultural and industrial products. This sits well with Australia’s current focus on innovation, driven by Prime Minister Malcolm Turnbull.
But the potential of biodiversity has been overlooked.
Animals and plants constitute a very small part of our native biodiversity (roughly 5%). The vast majority – fungi, bacteria and the enormous diversity of other microscopic organisms, including invertebrates – is a massive, largely unexplored economic resource.
The best known examples of commercial uses for biodiversity are the thousands of drugs secreted by bacteria and fungi. But others are examples of what is known as “bio-inspiration” and “bio-mimicry”, where wild species provide the blueprints for products.
While these products are of immense commercial value, the source species are rarely harvested in the conventional sense. Rather, a few specimens provide ample material for analysis.
So for microbes, invertebrates or plants, there is little concern that these industries are threats. For vertebrates, such as sharks, samples are either non-destructive or severely limited.
Some of the products such as spider silk and gecko feet are well known. But these are the tip of an iceberg.
Other innovations include fire detection inspired by charcoal beetles, clinical compounds from scorpions and leaping robots from locusts. In fact, bio-mimicry is huge in robotics, including the astonishing new field of “soft robots” modelled on tentacles, caterpillars and worms.
Products such as drugs can be sourced from single-celled animals and plants and from microbes of all kinds, even those that are currently uncultivable. Super-water-repellent materials, are sourced from the outer surfaces of organisms as different as insects and higher plants.
Then there is bio-mineralization: soft-bodied animals make very hard substances, such as the radula of marine snails, a tongue tough enough to drill rock. To make materials that strong, industry currently requires high temperatures and pressures, not to mention polluting chemicals.
The snails make their radula and shell from natural materials and at normal temperatures and pressures. How do they do it? Many labs around the world are struggling to find out.
How can exploring biodiversity help conserve it?
First, much as charismatic animals such as tigers and whales are used as icons for conservation, so can species that we use for developing products – but with the added grunt that they are central to the economy. These are very sexy stories; fascinating tales of the transformation of natural phenomena into industrial products.
Australia’s Biodiversity Conservation Strategy states that we must “engage all Australians” to save biodiversity. But leaving out biodiversity and industrial products is a massive lost opportunity for engagement.
Second, as biodiversity products come from any kind of organism from any kind of ecosystem, these growing industries require the conservation of that resource. This would greatly expand the current conservation focus on a few charismatic species.
Third, much of biodiversity exploration research is overseas. Some Australian scientists and engineers are involved, for example, in utilising the arrangements of plant fibres to inspire lightweight strengthening of aircraft engines. However, it is hard to find the promotion of this exciting research in any policy nation-wide; political, economic or scientific.
Given Prime Minister Turnbull’s focus on innovation, and given that Australian biodiversity is both vast and unique, overlooking biomimicry and its related industries is another lost opportunity for both conservation and the national economy.
Scientists and engineers inside many industries are forging ahead with exploration for biodiversity products in many, non-destructive and highly imaginative ways all over the world.
It’s time our governments and conservationists wised up.
Andrew Beattie, Emeritus Professor