Multiple studies have associated the increasing global temperature with human activities. For instance, the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC) revealed that human emissions and activities have caused around 100% of the warming observed since 1950. In its summary, the policymakers said that is “extremely likely that more than half of the observed increase in global average surface temperature” from 1951 to 2010 was caused by human activity.
According to Carbon Brief, a UK-based website designed to improve the understanding of climate change, both in terms of the science and the policy response, “extremely likely” meant that there was between 95% and 100% probability that more than half of modern warming was due to humans. The 2017 US fourth national climate assessment also found out that between 93% to 123% of observed 1951-2010 warming was due to human activities. Unfortunately, the impacts of the continuous warming of the planet have become more evident than ever. Both humans and wildlife are already experiencing higher temperatures in many countries across the world.
Global Warming Impacts on Animals
A 2019 study revealed that the Earth’s natural life-support systems are declining, with half of the natural ecosystems now destroyed and a total of a million species at risk of extinction. Animal populations have fallen by 60% since 1970, estimates have shown a number of natural ecosystems are now destroyed and a total of a million species are at risk of extinction. Aside from that, the largest creatures from all inhabited continents apart from Africa have been wiped out by humans over the last 125,000 years.
According to The Guardian, a British daily newspaper, the study suggests that a sixth mass extinction of life on Earth is underway. “This study predicts extinction rates that dwarf those recorded between recent ice ages and suggests that larger species are the most vulnerable. I wouldn’t be surprised if the situation for many larger animals is worse than the researchers suggest as their decline is exacerbated by selective poaching and the illegal wildlife trade,” author Chris Carbone from the ZSL Institute of Zoology in London said.
The researchers also revealed that larger animals are particularly vulnerable to humans because they are more frequently targeted and need much more wild space to survive. Their existence is important creating stable and productive ecosystems, thus, their extinction will be a great loss. “It is worrying that we are losing these big species when we don’t know their full role. Without them, things could begin to degrade quite quickly. Ecosystems could start to collapse and become not what we need to survive,” lead author Robert Cooke said.
The key impact of global warming on wildlife is habitat disruption, which is mainly due to the changes in temperature and water availability. While these affected wildlife populations can sometimes move into new spaces and continue to thrive, many land areas have already been occupied by humans. Also, many scientists have agreed that global warming is causing a shift in the timing of various cyclical events in the lives of animals. For instance, many birds have altered the timing of long-held migratory and reproductive routines due to the warming climate.
The Shrinking Effects of Global Warming
To respond to the growing impacts of global warming, many animals have modified the way they live and shifted the timing of their breeding cycles. But aside from altering their location and behaviors, the physical stature of some organisms is also affected. A study published in Nature Climate Change showed evidence for past and present downsizing of organisms in response to warming environments and how these changes could affect ecosystems as well as human health.
The researchers reported that fossil evidence suggests that organisms ranging from diatoms to ground squirrels have shrunk when the Earth warmed over the last 65 million years. According to Gizmodo, an environmental news website, the size of European House Sparrows living in Australia and New Zealand were found to have corresponded with their region’s maximum summer temperature through shrinking. Another research that studied zebra finches found similar results: higher temperatures mean smaller finches.
While scientists are not yet sure why the difference in size occurs, they suggested that excess heat causes changes in baby birds’ development..“Higher temperatures are somehow stressing the bird, which is either resulting in them not growing as well, or maybe there’s some sort of feedback loop where it’s hot, so the bird’s body starts investing fewer resources in growth. Maybe it wants to be slightly smaller and lighter to be better able to lose heat in those really hot conditions,” Sam Andrew, a doctoral candidate at Macquarie University in Sydney, said.
Multiple studies of different species have also found the same results. For instance, at least 22 beetle species were getting smaller when confronted with higher temperatures; six different species of salamanders have gotten smaller between 1950 and 2012, and Alpine chamois mountain goats today weigh about 25% less than their 1980 peers. Marine species are not immune to this change. Previous studies have found a shrinking trend in fish due to warming temperatures. One study predicted as much as a 30% reduction in size per one degree Celsius increase in water temperature for some species.
“I find it very interesting—or concerning, depending on which way you look at it. Across different species in different environments, with different life history characteristics—such as cold-blooded and warm-blooded—there seems to be a general trend that the size is shrinking,” Alan Baudron, a biology research fellow at the University of Aberdeen, said.
To dive deeper into these studies, researchers from the University of Erlangen-Nuremberg investigated how prehistoric organisms such as belemnites reacted to climate change. Paleontologist Dr. Patricia Rita explained that these organisms are particularly interesting because they were very widespread for a long time and are closely related to the squid of today. According to Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, their fossilized remains can be used to make reliable observations.
The findings published in the online publication Royal Society Open Science show that belemnites have shrunk significantly when the water temperature rose as a result of volcanic activity approximately 183 million years ago, confirming the hypothesis that climate has a significant influence on the morphology of adult aquatic organisms. However, many scientists clarified that the warming-shrinking trend does not apply to every organism, particularly those with longer generation times or some at higher latitudes.