How Is Climate Change Deadly For Australia's Koala Population?

By Benjamin Elisha Sawe on November 17 2019 in Environment

A mother koala with her baby on eucalyptus tree.
A mother koala with her baby on eucalyptus tree.

Koala is one of Australia’s most iconic animals. The furry and cuddly marsupials are found mainly in the eastern part of Australia. Koalas are considered fussy eaters as they only feed on 40 to 50 species of eucalyptus found in Australia. The koala (a term that means “no drink” in the native Australian language) is adapted to get much of their nutritional and moisture needs from eucalyptus leaves. The koalas were formerly hunted to near extinction in the early 20th century for their fur. The species is currently struggling to survive as a result of disruptive human activities and climate change-induced habitat loss due to bushfires and droughts. Climate change is also cited as a leading contributor to the declining moisture content and nutritional value of eucalyptus leaves. Over that last 20 years, the Koala population has witnessed a steep decline. The Australian Koala Foundation estimates that there are about 45,000 to 90,000 koalas in the wild. Some of the regions that have experienced the sharpest declines include Queensland, which witnessed a 40% drop in its koala population in the last 20 years and New South Wales, which lost nearly 33% of its Koala population in the same period.

Effects of climate change on the koala’s habitat

Studies have shown that climate change is contributing significantly to warmer and drier conditions that are conducive to wildfires. In 2009, the world got a hint of the devastating effects of climate change on the koala population when raging forest fires tore through Victoria, killing over 170 people and countless koalas. A video of a parched koala called Sam being helped to hold a bottle of water in her burnt hands by a firefighter immediately went viral making her a video star. Unfortunately, she did not live for long as veterinarians later discovered that she had severe cysts as a result of chlamydia, a disease plaguing wild koalas that likely crossed to the koala population from imported livestock. The ongoing (2019) forest fire blaze has so far killed three people, destroyed more than 150 homes, displaced thousands, and ripped through nearly 2,000 hectares of koala breeding grounds in New South Wales, killing hundreds of koalas. A seven-day state of emergency was declared across the state starting November 11, 2019, with that latest incident receiving the “catastrophic” rating from the Rural Fire Service. Rescuers have termed the incident as particularly tragic due to the diverse breed of koalas that were in the area.

While wildfires are not uncommon in Australia, the koala’s coping mechanism is not considered adequate. When wildfires occur, koalas typically climb to the top of trees and curl into a ball. When fires are less intense, the fur is burnt off slightly and regrows after some time, but when the fire is more intense, koala fatalities are almost unavoidable. Unfortunately, as a result of climate change, scientists predict that bush fires are likely to increase in frequency and intensity and last longer going into the future if drastic action is not taken to curb climate change. The wildfires currently ravaging the country began in September 2019, a deviation from the usual beginning of the fire season in December to February. Analysts have blamed extreme weather events driven by climate change for the more frequent, intense, and earlier bushfires in the country.

Rising carbon dioxide levels

The koala’s picky diet is a result of the different nutrient and anti-nutrient ratios found in the various species of eucalyptus. For example, some eucalyptus species are known to have high protein levels but also have anti-nutrients such as tannins that bind the protein making it unusable by the koala. Laboratory tests by scientists at the Australian Academy of Science have found that the ever-rising carbon dioxide levels and the increasing temperatures as a result of climate change are affecting the nutrient and anti-nutrient ratios in eucalyptus trees, which koalas are dependent on. Carbon dioxide concentration levels globally have risen by 107 ppm since the industrial revolution to 387 ppm recorded today. The concentration is expected to reach between 500 and 600 ppm by 2050. High carbon dioxide concentration levels in the atmosphere alter the levels of nutrients and “anti-nutrients” (substances that are either toxic or those that interfere in the digestion of nutrients) in the leaves of the eucalyptus tree. The rising levels of carbon dioxide mean that the levels of anti-nutrients (built from carbon) are likely to increase relative to the level of nutrients, thus further limiting the diet options of the koalas. Scientists reckon that at the current rate of carbon dioxide concentration, what is today considered as a suitable koala habitat might gradually turn unsuitable in the not-so-distant future.

Effects of temperature increase on food supply

The continued increases in temperature due to global warming have been found to affect the species of eucalyptus prevalent in certain areas. Eucalyptus species have different sensitivities to temperature, with some of the most sensitive species experiencing changes due to as little as a 33.8 degree Fahrenheit shift in mean annual temperature. With temperatures increases as a result of climate change, vulnerable species could be outcompeted by other less sensitive species. If the less sensitive species are unsuitable for the koala, then the facade of forests will conceal the nutritional habitats of the koalas. Scholars have also found that climate change is leading to changes in the nitrogen and water content of their sole source of nutrition – eucalyptus leaves. According to research, climate change leads to a significant decline in the nutritional value of eucalyptus leaves and a reduction in the leave’s moisture content. As a result, more koalas are risking their lives by leaving their trees in search of water and food. Such behavior leaves them vulnerable to predators and death as a result of being hit by cars.

Heat stress

A study summarised in the Global Change Biology journal predicted that a significant number of koala habitats, especially in Queensland, would become inhospitable by 2070. The researchers found that future changes in temperature and a decline in rainfall would affect the amount of water stored in eucalyptus leaves (the primary source of a Koala’s hydration). As a result, extreme heat stress will probably lead to the death of koalas in several locations. The research also found that koalas closer to coastal regions had high chances of survival compared to that deeper inland. Unfortunately, the koalas also have to compete against humans keen on development and agriculture for such areas. The findings are supported by those conducted at the Global Change Institute at the University of Queensland, which found that koalas have a temperature threshold of 98.6 degrees Fahrenheit. When exceeded, as a result of changes in weather and climate change, heat stress was found to affect koalas as a result of inadequate water for thermoregulation. Koala habitat ranges are also expected to continue moving eastward towards the coast, where there is a more moderate climate. According to Christine Hosking, a biologist at the University of Queensland, there is already evidence that koala populations have declined by nearly 80% in some areas that are more inland.

Rising sea levels

According to Dr. Rebecca Montague-Drake, an ecologist with the Port Macquarie Council in New South Wales, 14 % of areas currently inhabited by koalas will experience saltwater inundation in the next 50 years, and that is expected to climb to 22% in the next century. Rising salinity from floods and bigger tides due to climate change is expected to increase the level of toxins in the eucalyptus tree, thus further reducing the food available to the koala. Koalas are already walking a tightrope with the limited species of eucalyptus they eat, the high levels of toxins found in the leaves, and the amounts of toxins they can extract from the leaves. Ecologists predict that the 621-mile coastal strip between Jervin and Moreton bay is likely to lose a significant portion of its eucalyptus trees in the future, further reducing koala habitats.

Can koalas adapt quickly enough to climate change?

Scientists are not optimistic about koala’s ability to adapt to climate change, mainly because the changes are occurring faster than the koalas have ever experienced in the past. The limited genetic variations in their populations due to substantial population reductions and years of inbreeding further diminish the koala’s ability to adapt. Some of the suggested changes that might occur to cope with increasingly nutrient-poor and tannin-rich diets include koalas spending more time eating and increasing their leaf and tree choice. Their adaptation to other aspects of climate change events such as bushfires is, however, limited.

Initiatives to help koalas deal with climate change

In 2016, researchers at the University of Sydney placed drinking stations in koala habitats in New South Wales. The objective was to supplement water sourced from eucalyptus leaves. To their surprise, the koalas regularly visited the water stations. In recent years, koalas have also been observed to climb down trees and visit human settlements in search of water and food. The study, coupled with current observations, have prompted the local authorities to adopt water stations as a strategy to help koalas deal with increased temperatures and drought as a result of climate change. However, it is worth noting that taking measures aimed at mitigating climate change is the only sustainable solution to global warming-related challenges facing koalas.

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