Disappearing and unwelcome lives

 

 

By Science Columnist Ho-Gwan Ko

 

 

The lives on the Earth have suffered several major crises since birth: mass extinction. Extinction means that individuals of a given species completely disappear for some reason. When more than 70-80% of a species become extinct in a short period, it’s called a mass extinction.

The most typical examples include the Permian mass extinction and the end-Cretaceous mass extinction, which is well known for the extinction of the dinosaurs. Although it’s difficult to discover the exact causes of the hundreds of millions of years-old mass extinctions, scientists attribute them to climate change resulted from catastrophes such as meteorite impacts and volcanic eruptions.

Now, what could cause another mass extinction event is happening. While the causes of the mass extinctions in the past were natural phenomena, the culprit of today’s ongoing extinction is humans. People have gradually dominated the planet, exterminating many animals – sometimes by excessive hunting and sometimes by destroying habitats. Recently, human-induced climate change is taking its toll.

The Bramble Cay melomys is a fauna that lives, or rather lived on a small island in the Torres Strait in northern Australia. This small species used to thrive when it was first discovered, but the number gradually decreased to the extent that they were rarely found in the 2010s. In 2016, it was officially declared that they went extinct. The fundamental cause of the extinction was rising sea levels caused by global warming. The reason why this is worth noting is that it’s the first mammal to have become extinct due to human-caused climate change.

Climate change affects all life on Earth. Animals and plants can’t live in their original homes and have no choice but to move to another place or even become extinct. One of the typical examples is the polar bear. Adapted to the cold Arctic environment, polar bears hunt animals like seals on ice. However, climate change has reduced the Arctic ice cover, making it difficult for polar bears to hunt. The distance they have to travel to hunt has become longer, and there is a risk that the permafrost will melt as the winter warms, destroying their subterranean home. It’s estimated that there are about 20,000-30,000 polar bears left; if this continues, they will become extinct by 2100.

 

 

▲ If we don't stop global warming, polar bears will become extinct.

Do you think you can’t relate to this crisis because people don’t live in the North Pole? In early 2020 when COVID-19 emerged as a global pandemic, there was another problem that plagued people: a swarm of grasshoppers numerous enough to cover the sky. In Africa, swarms of desert locusts damaged crops in a large tract. More cyclones were formed than before as the sea water got warmer, and the temporary humid climate made desert locusts flourish.

The warmer the weather, the more pests such as mosquitoes and ticks. Mosquitoes love a warm, humid environment, and the time from egg to adult becomes shorter at higher temperatures; it usually takes 19 days when the temperature is 22°C, but it reduces to just 12 days at 26°C. This means an increased number of mosquitoes. As we have more warm days throughout the year, we will suffer from mosquito bites for a longer period.

Plants are also affected by climate change. Since they can’t move like animals, they are more vulnerable. As for crops grown by humans, the planting zones change over time. They are shifting north, bringing crops that used to be grown only in the south to the north.

Another problem is that the flowering periods change. When spring comes and the temperature rises, several plants bloom and bear fruit. What if this happens earlier and insect pollinators can’t get the timing? This leads to problems in the reproductive activity of plants. Animals that feed on insects and fruit will also suffer. Even if fruit is born, it may die due to abnormally low temperatures.

Climate change also affects the ecosystem in a way that we can’t even expect. For instance, the number of parasites can change if the number of host animals changes or larval habitats are destroyed due to climate change. In 2017, researchers at UC Berkeley reported that 30% of parasites will become extinct by 2070. Although some parasites harm humans, they also play an important role in the ecosystem. If parasites disappear, the ecosystem can be disrupted.

As discussed so far, climate change affects every corner of the ecosystem. As climate change continues, we may see unexpected adverse effects. If we can’t stop climate change, we could be the next mass-extinct species on the Earth. This mass extinction will include ourselves.