A third of northern NSW’s ancient and irreplaceable rainforests burnt last year. Buffers need to be established, and weed control undertaken, to increase their resilience.
Though until we stop global heating burning will become more frequent and intense, eroding the extent, viability, and biodiversity of our residual rainforests, along with our future.
The impacts of rising temperatures, droughts and heatwaves on rainforests have been increasing. When mature rainforests start burning we know the situation has become dire, as they are not adapted to fire. Burning of rainforests is akin to the bleaching of coral reefs.
The NSW Government’s mapping of fire extent and canopy scorch shows that some 160,000 hectares (35%) of north-east NSW’s 462,000 ha of rainforests were burnt last fire season.
These rainforests are descendants from over 70 million years ago when Australia was clothed in rainforest as part of the supercontinent of Gondwana. They have been in decline since Australia separated from Antarctica and became increasingly arid around 30 million years ago, with fire a major diver over the past 130,000 years. Increased burning accelerated their loss after the arrival of people around 50,000 years ago.
The arrival of Europeans resulted in extensive clearing and degradation of the surviving rainforests. Widespread logging changed their structure, dried them out and increased their flammability. Decades later many stands are still struggling to recover.
The relatively small remnants left are packed with survivors from the ancient forests. Rainforests now cover only about 0.25 per cent of Australia, yet they contain about half of our plant species and a third of our mammals and birds.
The exceptional importance of NSW’s rainforests is recognised by parts being created as the Gondwana Rainforests of Australia World Heritage Area.
Rainforest’s resilience to fire is primarily due their dense canopies maintaining a moister microclimate. Last year was Australia’s hottest and driest year on record,resulting in north-east NSW’s rainforests becoming unusually dry and flammable.
It is frightening that with only one degree of global heating over a third of these priceless relicts burnt in one year. Across the fire-grounds most leaf litter, logs and understorey plants were burnt, along with their inhabitants. Many tree bases were damaged. Even riparian areas burnt.
Most worrying is the significant loss of large canopy trees, hundreds of years old, across 125,000 ha of rainforests, with 34,000 ha of this losing most canopy trees. Images show the impacts. Those areas heavily burnt will struggle to regenerate.
Some stands are unlikely to ever recover, further diminishing our rainforest heritage.
Some 230,000 ha within 100m of rainforest stands also burnt. These encompass vital buffers, characteristically with an overstorey of eucalypts and an understorey of hardier rainforest species.
These transition zones are essential to maintain rainforest microclimates, reduce fire threat, and provide complementary habitat and resources for some species. Their degradation increases the drying of rainforests and vulnerability to the next fire.
Fifty seven of the Commonwealth’s 113 most fire affected animal speciesoccur in north-east NSW’s forests, many in rainforests and their buffers. There are many more rare and endemic plant species that have had significant portions of their populations burned.
It is too early yet to assess the full consequences of the fires on rainforests, though there can be no doubt that they have inflicted significant damage, affected their viability and increased their vulnerability to further burning.
With climate heating increasing droughts, temperatures, heatwaves and extreme fire weather, many of our relictual rainforests are under a looming threat to their continued existence.
The obvious priority is to assess the impacts of the fires on the forests and those species whose habitat was most affected. Once we know how badly they have fared, we then need to monitor their recovery and provide help where needed.
In the interim, to reduce future threats the NSW Government needs to stop logging and clearing rainforest buffers, and remove weeds and debris from past logging. As a minimum, 50m buffers (one tree height) should be applied around all mapped rainforest stands from which logging and clearing are excluded.
Lantana has been the scourge of rainforest, invading areas where canopy has been reducedby logging or fire, suppressing regrowth, increasing flammabilityand initiating dieback in adjoining logged eucalypt forests.
The intensity of the fires has killed lantana over large areas, creating an opportunity to control it before it takes over again. This opportunity must be capitalised on if we want to increase the resilience of rainforests.
It is a bad idea to increase fuel reduction burning in these wet refugia where fires are naturally rare. More frequent fires in the vicinity of rainforests will just make the situation worse by drying and increasing the flammability of their vital buffers.
While we can help the rainforests recover from the recent fires, and enhance their resilience, their salvation lies in urgently stopping runaway climate heating.
We need our forests more than ever, not just because of their intrinsic worth and beauty, but for the ecosystem services they provide us, such as generating rainfall, cooling the land, calming winds, regulating streamflows, and capturing and storing the carbon we emit.
Smoke from last year’s Australian bushfires released an estimated 400 million tonnes of carbon dioxide to the atmosphere, doubling our annual emissions. Vast quantities of carbon were also lost through erosion. The loss of so many older trees has also diminished the ability of our forests to absorb atmospheric carbon. It will take forests decades to regain the carbon they lost.
For our carbon accounting we rely upon the world’s forests absorbing around a third of our carbon emissions, though intact tropical rainforests are taking up a third less carbon than they did in the 1990s, owing to the effects of increasing droughts and heatwaves on trees, and their continued loss through logging, clearing and burning.
We cannot afford to allow this downward trajectory to continue if we want to give rainforests and ourselves a future. We need to urgently protect our forests, and start rehabilitating them, to improve their resilience to further climate changes and increase their carbon storage to limit future impacts. Stopping logging of public native forests is a logical first step.