ecological imbalance

Death of a landscape: why have thousands of trees dropped dead in New South Wales?

2,000 square km of forest have dropped dead in New South Wales, indicating big changes to the environment.

Trees die – that’s a fact of life. But is the death of an entire iconic landscape of Eucalyptus in the Cooma-Monaro region of New South Wales natural?

For over a decade, large stands of Eucalyptus viminalis, commonly known as Ribbon Gum or Manna Gum, have been gradually declining in health, and now stand like skeletons in huge tree graveyards.

In our recently published survey we found the affected area to cover almost 2,000 square km, about the size of the area burnt in the devastating Ash Wednesday bushfires in Victoria or more than the area covered by the 2003 Canberra fires.

Within this area, almost every Ribbon Gum is either dead or showing signs of severe stress and dieback, with thinning crowns full of dead branches. Other tree species seem to be surviving, but this smooth-barked gum with its characteristic ribbons of peeling park, once the dominant tree of the Monaro, now seems set to disappear from the landscape.

Map of dieback observed during survey

Source: Ross and Brack 

Why do trees die?

Dieback is not an unusual phenomenon in Australia. Rural dieback first achieved widespread notoriety in the New England area of NSW during the 1970s and 1980s. This dieback was attributed to agricultural practices such as grazing, fertilisation and understorey clearing that upset the balance of insects and their predators.

The resulting insect population explosion led to repeated defoliation, which over several years exhausts the trees’ ability to recover. In the case of the Monaro dieback, the ultimate cause of death seems to be an infestation of the (native) Eucalyptus Weevil (Gonipterus sp.), which have been observed in large numbers on the few surviving trees.

Although dieback is often associated with insect attack, it seems that the underpinning reasons are much more complex.

In our study, Ribbon Gums appeared to be uniformly dead or showing signs of severe dieback regardless of their local environment. Areas that had been fenced off or with no other major disturbance might have been expected to be more resilient to dieback, but were as badly affected as those in paddocks that had been fertilised or grazed.

Similarly, absence or presence of recent fire or pasture improvement made no difference to the trees' health. Asking graziers to change their practices, or fencing out reserves doesn’t appear to be effective in saving the Ribbon Gum.

The Millennium drought may also have played a role, given that the onset of the dieback coincided with a significant drop in rainfall.

Large dieback events are being observed more frequently in Australia and around the world, and often been attributed to severe droughts.

In Western Australia it has been reported that jarrah, banksia and tuart woodlands experienced widespread collapse due to extreme temperatures and drought, causing a permanent shift in species distributions.

The Monaro region has a harsh climate, with extremes of temperature and very low rainfall due to the rain shadow of the Snowy Mountains. Ribbon Gums normally grow in wetter areas and the Monaro is at the edge of their climatic range, so the Millennium drought and ongoing climate change may have pushed the trees beyond a critical threshold.

A vision of future forests?

Whatever the cause, the size and impact of dieback is comparable to the heightened bushfire threat in Australia - but unlike expected recovery after a fire, species lost to dieback may never regenerate. This potential impact should raise significant alarm, but to date, the Monaro dieback has received relatively little attention or action.

What is also particularly concerning is the speed at which this dieback occurred, leaving other species little chance to adapt. There is no evidence that other tree species will naturally fill the gap, and attempts to replant local species have been largely unsuccessful, so we may need to introduce replacements.

Species from more arid areas may be needed to tolerate the predicted future climate and provide some of the ecosystem function that has been lost - but how do we select which species to introduce?

The Monaro with its dead hulks of trees may be a stark vision of the future, especially for those thousands who pass on their way to the ski fields during ever shorter snow seasons.

However it also emphasises the need to better predict and prepare for dieback events, particularly where a dominant species is on the edge of its range. We need to determine what species and active management practices we need to replace our missing tree icons.

We will have to decide what values we place on trees and forests, and plan how we want the landscape to look in 100 years’ time.

Cris Brack, Assoc Professor Forest measurement & management, Australian National University and Catherine Ross, PhD candidate, Australian National University

This article was originally published on The Conversation.

We welcome your comments at
Sponsored Content BY 

Some of the most significant innovations in automotive history made their debut in this iconic automobile

The latest version features India's first BS VI norms-compliant engine and a host of 'intelligent' features.

The S-Class, also known as Sonderklasse or special class, represents Mercedes Benz’ top-of-the-line sedan line up. Over the decades, this line of luxury vehicles has brought significant automotive technologies to the mainstream, with several firsts to its credit and has often been called the best car in the world. It’s in the S-Class that the first electronic ESP and ABS anti-lock braking system made their debut in the 20th century.

Twenty first-century driver assistance technologies which predict driver-behaviour and the vehicle’s course in order to take preventive safety measures are also now a staple of the S-Class. In the latest 2018 S-Class, the S 350 d, a 360-degree network of cameras, radars and other sensors communicate with each other for an ‘intelligent’ driving experience.

The new S-Class systems are built on Mercedes Benz’s cutting-edge radar-based driving assistance features, and also make use of map and navigation data to calculate driving behaviour. In cities and on other crowded roads, the Active Distance Assist DISTRONIC helps maintain the distance between car and the vehicle in front during speeds of up to 210 kmph. In the same speed range, Active Steering Assist helps the driver stay in the centre of the lane on stretches of straight road and on slight bends. Blind Spot Assist, meanwhile, makes up for human limitations by indicating vehicles present in the blind spot during a lane change. The new S-Class also communicates with other cars equipped with the Car-to-X communication system about dicey road conditions and low visibility due to fog, rain, accidents etc. en route.

The new S-Class can even automatically engage the emergency system when the driver is unable to raise an alarm. Active Emergency Stop Assist brings the car to a stop if it detects sustained periods of inactivity from the driver when Active Steering Assist is switched on. If the driver doesn’t respond to repeated visual and audible prompts, it automatically activates the emergency call system and unlocks the car to provide access to first responders.

The new Mercedes-Benz S 350 d in India features another notable innovation – the country’s first BS VI norms-compliant car engine, in accordance with government regulations to control vehicular pollution. Debuting two years before the BS VI deadline of 2020, the S 350 d engine also remains compatible with the current BS IV fuels.

The S 350 d is an intelligent car made in India, for Indian roads - in the Mercedes Benz S-Class tradition. See the video below to know what drives the S-Class series by Mercedes Benz.

To know more about the 2018 S-Class, click here.


This article was produced by the Scroll marketing team on behalf of Mercedes Benz and not by the Scroll editorial team.