Saving Our World–Chapter Thirteen–How Does Climate Change Affect Our Animal Life?

Global warming, scientists say, is responsible not only for shrinking ice caps but also for a surge in extreme weather that is causing heat waves, forest fires, and droughts. The polar bear standing on a chunk of shrinking ice, apparently stranded, has become a familiar image, a symbol of the devastating effects of climate change.

This image is somewhat misleading since polar bears are powerful swimmers and climate change will primarily affect them by restricting access to prey. Nevertheless, researchers agree that even small changes in temperature are enough to threaten hundreds of already struggling animals. Up to half of the animal and plant species in the world’s most naturally rich areas, such as the Amazon and Galapagos, could face extinction by the turn of the century due to climate change, according to a study published in the journal Climate Change.

More than 700 bird and mammal species are being negatively affected by climate change, according to a massive international study that synthesized 130 reports.

Climate change is such a diffuse and delayed phenomenon that it has been hard in the past to disentangle it from other factors threatening wildlife. But the report’s authors believe that accumulated research now speaks for itself — climate change is affecting animals at a far greater rate than anticipated.

The collated figure is much higher than previous predictions, and could be just a fraction of the total threat represented by climate change.

“This under-reporting is also very likely in less studied species groups,” James Watson of University of Queenland’s School of Earth and Environmental Sciences, told Science Daily. “We need to greatly improve assessments of the impacts of climate change on all species right now.”

“We need to communicate the impacts of climate change to the wider public and we need to ensure key decision makers know significant change needs to happen now to stop species going extinct,” he said. “Climate change is not a future threat anymore.”

Out of 873 mammals, nearly half have had negative responses to climate change and 23% of 1,273 studied birds had negative responses.

Meanwhile, just 7% of adversely affected mammals and 4% of adversely affected birds are considered endangered by climate or severe weather events by International Union for the Conservation of Nature Red List of Threatened Species.

Climate change affects animals in different ways. For instance, African elephants are highly sensitive to changes in temperatures and habitats and susceptible to new diseases that can be spread by a changing environment. They also needs large amounts of water to survive, something that is threatened by increasing spells of drought and desertification throughout the world.

Polar bears, meanwhile, depend on polar ice that is rapidly melting to access food.

Green sea turtles base their reproduction habits on temperature changes and as waters heat up around the world, this delicate process is threatened.   

Marine life more generally is experiencing profound changes to the composition of water quality as ocean acidification — the process of water absorbing carbon dioxide — intensifies. Coral reefs, in particular, are basically dissolving like antacid.  

Many birds depend on environmental cues to guide their migration patterns and these cues — often temperature or environmental changes — are being disrupted.

Climate change is a cumulative threat that intensifies as it gradually unfurls. The emissions that are released today affect the environment decades from now. Since emissions have been accelerating over the past several decades, the worst effects of climate change are likely yet to come.

Animals, meanwhile, adapt at a much slower rate. Unlike humans, animals can’t just pack up and start over somewhere else. They’re intimately connected to their habitats, and as these habitats disappear or become irrevocably compromised, the future of far too many animals will be at risk.


Biodiversity is the sum of all life on earth. Every single individual lifeform from the smallest bacteria in the soil to the largest whale in the sea, is a component of Earth’s biodiversity. But biodiversity doesn’t stop at the individual. Biodiversity is also the relationships between these lifeforms and their habitat. That includes the relationship between plankton and whales that help produce oxygen in the atmosphere, seeds and rhinos that help plant forests, and bacteria and plants that change the chemistry of soils.


Biodiversity is an abbreviation of the term “biological diversity” which was coined in the mid-1980s with the help of the legendary tropical biologist, Thomas Lovejoy. (See what Thomas Lovejoy has to say about protecting the planet’s biosphere.)

In the sciences, biodiversity is measured at several levels: genetic, species, communities, and ecosystems.

Humans are very much a member of the biodiversity community, and our own cultural diversity is increasingly recognized to be a product of local biodiversity. Culture is closely connected to the wild nature from which human communities emerge. The term “bio-cultural diversity” describes the relationship between human culture and the surrounding ecology.

Biodiversity tends to be far higher in the tropics than in cold, polar regions, meaning that in the tropics there are the most species, more genetic data, and more complex ecological interactions. Still, even the coldest, darkest regions, from the polar seas to the deepest caves, are rich in lifeforms. And each and every one of these lifeforms contributes something important to the chemistry of their, and our, environment.

The highest quality biodiversity is often found in two types of places: protected area wildlands and those territories stewarded by Indigenous Peoples.


Earth’s biodiversity is its most valuable and most necessary resource. Biodiversity is the primary source of Earth’s biosphere – the life web that produces everything humans need most: food, water, many modern medicines, and air. While other planets are likely rich in minerals of high monetary value here on Earth, no other planet that we know of have the conditions necessary for human civilization.

Earth’s biodiversity is the very basis for our own survival. This is demonstrated repeatedly, across the planet, at the macro and microscopic scale. Without plants, there would be no oxygen. Without bees, many of our crops would vanish. Other benefits of biodiversity are even more fundamental. The hardwood trees in the rainforests that are our most effective above-ground carbon sinks are also the product of the relationship between seeds and the fruit-eating animals that eat them. Trees are up to 500x more likely to germinate when the seeds have first passed through the digestion system of a bat, monkey, or elephant.

Microscopic biodiversity in our soils creates the chemical conditions necessary for healthy, abundant, and sustainable crops. Many new medicines are found in nature, including cancer fighting fungi and pain killing tree resins.

Economically, the services provided by biodiversity are estimated to be double the world’s annual GDP – although this number is difficult to calculate as many of biodiversity’s life-giving services cannot be replicated at scale by human technology.


The current projection for biodiversity is grim. In a recent report by the United Nations, an international coalition of scientists concluded that within the next 80 years, we are on track to lose over one million known species. That is one species in eight. In addition, the populations of individuals species have plunged. Tigers have lost 97% of their populations, migratory birds are estimated to have lost approximately 70% of their populations. In the span of only a few decades, the biomass of humans and our livestock has come to total 24x more than that of all other wild mammals!

The single biggest threat to biodiversity is habitat loss, linked to food production on land and in the sea. Biodiversity needs space to survive. Every animal needs a home. That home is wilderness. When we remove wildlands and convert them into industrial production spaces, we simultaneously subtract the landscapes needed for life production. The landscapes we depend on are for our own survival.  Rising temperatures affect vegetation, food sources, access to water and much more. Ecosystems may become uninhabitable for certain animals, forcing wildlife to migrate outside of their usual patterns in search of food and livable conditions, while causing other animals to die off. 

For example, if rates of habitat loss and fragmentation due to human development and global warming continue—combined with deaths from poaching—we could lose Africa’s elephants in the next 40 years. 

Habitat Disruption

The key impact of global warming on wildlife is habitat disruption, in which ecosystems—places where animals have spent millions of years adapting—rapidly transform in response to climate change, reducing their ability to fulfill the species’ needs. Habitat disruptions are often due to changes in temperature and water availability, which affect the native vegetation and the animals that feed on it.

Affected wildlife populations can sometimes move into new spaces and continue to thrive. But concurrent human population growth means that many land areas that might be suitable for such “refugee wildlife” are fragmented and already cluttered with residential and industrial development. Cities and roads can act as obstacles, preventing plants and animals from moving into alternative habitats.

A report by the Pew Center for Global Climate Change suggests that creating “transitional habitats” or “corridors” could help migrating species by linking natural areas that are otherwise separated by human development.

Shifting Life Cycles

Beyond habitat displacement, many scientists agree that global warming is causing a shift in the timing of various natural cyclical events in the lives of animals. The study of these seasonal events is called phenology. Many birds have altered the timing of long-held migratory and reproductive routines to better sync up with the warming climate. And some hibernating animals are ending their slumbers earlier each year, perhaps due to warmer spring temperatures.

To make matters worse, research contradicts the long-held hypothesis that different species coexisting in a particular ecosystem respond to global warming as a single entity. Instead, different species within the same habitat are responding in dissimilar ways, tearing apart ecological communities millennia in the making.

Natural disasters: Already today we face a five-fold increase, compared to 50 years ago, in climate and weather-related natural disasters such as droughts, wildfires and hurricanes. These disasters cause catastrophic loss of life and habitat for people, pets and wildlife.  

Australia’s Black Summer bushfires (2019–20), for example, burned 186,000 square kilometers (72,000 square miles) and are estimated to have killed or displaced three billion koalas, kangaroos and other animals. 

When we lose biodiversity, we reduce our ability to fight climate change, grow sustainable and healthy crops, have access to clean and abundant water, prevent pandemics, and plan for a future for our children and grandchildren.

Humans need biodiversity. And because the decline in biodiversity is caused by humans, biodiversity now needs us to transform our behavior.

Effects on Animals Affect People Too

As wildlife species struggle and go their separate ways, humans can also feel the impact. A World Wildlife Fund study found that a northern exodus from the United States to Canada by some types of warblers led to a spread of mountain pine beetles that destroy valuable balsam fir trees. Similarly, a northward migration of caterpillars in the Netherlands has eroded some forests there.

Human-wildlife conflict: Climate change intensifies human-wildlife conflict through habitat loss and extreme climate events, forcing people and wildlife to share increasingly crowded spaces. As ecosystems change, people and wildlife roam farther in search of food, water and resources. Human-wildlife conflict often results in devastating impact for the animals affected.  

For example, jaguars sometimes prey on domestic animals and disrupt human livelihoods, leading to retaliatory killings that result in the further decline of already-dwindling jaguar populations. 

Extinction: The combination of challenges could cause many animals to go extinct. The world’s most vulnerable animals, including those already near extinction, will likely face the biggest threats.  

The North Atlantic right whale, for example, teeters on the brink of extinction, with an estimated 336 individual animals remaining, the lowest count in 20 years. A warming ocean, coupled with a failure to decrease conflicts with humans (vessel strikes and entanglement in fishing gear), could drive this species to extinction. 


Humans need wild nature in order to survive. The best solution for fighting climate change and ending the extinction crisis is to set aside enough space for nature to support healthy biodiversity. That means protecting at least half the planet’s land and and seas. Scientists conclude that if we do so by 2030 we can successfully avert the worst of the climate and extinction emergencies. (In some cases, we need more than half. Fragile ecosystems, like rainforests, need up to 80% protected or stewarded by local, sustainable communities.)

Protecting the planet at that scale may seem like a huge task, but in fact, this is a historic opportunity for us to transform the way we live with nature. Because we must protect half the entire planet, that means every region, every community, every individual is on the frontlines of conservation. You are on the frontlines of conservation, and you can make a difference.

The challenge is that while we need biodiversity and biodiversity needs us, most people around the world still don’t know about the critical importance of wildlands and the biodiversity they support. You can help change that and spark new hope for the future. When you share with your friends, families, and networks about biodiversity, you expand the possibility for a healthy and wild future, and give new reason to hope.

Our climate is changing, both naturally and due to human exploitation.

There is already undeniable evidence that animals, birds and plants are being affected by climate change and global warming in both their distribution and behavior. Unless greenhouse gas emissions are severely reduced, climate change could cause a quarter of land animals, birdlife and plants to become extinct.

Climate variability and change affects birdlife and animals in a number of ways; birds lay eggs earlier in the year than usual, plants bloom earlier and mammals are come out of hibernation sooner. Distribution of animals is also affected; with many species moving closer to the poles as a response to the rise in global temperatures. Birds are migrating and arriving at their nesting grounds earlier, and the nesting grounds that they are moving to are not as far away as they used to be and in some countries the birds don’t even leave anymore, as the climate is suitable all year round.

A sea level rise of only 50cm could cause sea turtles to lose their nesting beaches – over 30% of Caribbean beaches are used by turtles during the nesting season and would be affected. The already endangered Mediterranean Monk Seals need beaches upon which to raise their pups and a rise in sea level could there could damage shallow coastal areas used annually by whales and dolphins which need shallow, gentle waters in order to rear there small calves.

Humans have already destroyed many of the natural migrations of animals.

The migratory journeys of Wildebeest in several African countries are stopped by fences. Changing rainfall patterns are causing dams to be erected in some areas of our planet, not taking into account the migratory fish and mammals that annually migrate up river to breed and spawn and water birds which rely on wetland sites for migration are at threat from rising sea levels caused by human effects. On the other side of the coin, the atmosphere is sucking moisture from the land at a greater rate than ever before causing severe droughts in many countries which are now facing reduced crop production and major drinking water shortages.

Although it is thought that no species has yet become extinct exclusively because of climate change, many migratory and non-migratory species are expected to become extinct in the near future.

Rising Temperatures and Invasive Species

Rising temperatures risk destabilizing the balance between wildlife and their ecosystem. As plants adapt to changing warming patterns, usually by blooming earlier or shifting to cooler locations, the wildlife that has adapted to them will be forced to face new environments.

Some species will struggle to find nutritious enough food to fit their existing gut biomes. Pollinators, for example, must feed from flowers that are blooming earlier in the year. Other animals may find their habitats are no longer able to support their biology.

However, it is also possible that some animals will do better in a warmer climate. Those species will outcompete others, expanding their own territory and food sources. But not all wildlife belong where they flourish. When species adapted to their environments lose their natural advantages, that leaves room for invasive species to multiply in the changing environment. Emerald Ash Borers and Gypsy Moths are examples of invasive species commonly found in the National Capital Region that have devastated native communities.

Rushing water over rocks in a Catoctin Mountain Park cree
Big Hunting Creek at Catoctin Mountain ParkPhoto by Kent Walters

Native Brook Trout at Risk

Brook trout in the Catoctin Mountain Park offer a clear example of how climate change effects interact with invasive species spread. The brook trout is a freshwater fish species native to eastern North America, and it requires cold, clear stream habitats. Competing with the brook trout are nonnative brown trout which can tolerate higher temperatures.

Increases in air temperature are warming aquatic habitats, leading to an overall decrease in brook trout and giving the survival advantage to the invasive brown trout. A 2017 study from the US Geological Survey found that brook trout are capable of adapting and foraging for food in warmer waters but not when they’re competing against brown trout.

Flooding and Loss of Habitats

Increased precipitation from climate change is contributing to more frequent and extreme weather events such as flooding. The higher frequency of flooding has detrimental effects on wildlife because they can destroy key pieces of ecosystems and habitats.

There is the obvious destructive effect that floods have on the environment—such as flooded land and burned forests—but they also have other lasting effects like severe water pollution. Speedy flood waters spend little time in a purification place (like in the ground or in a wetland) so the surface flow doesn’t lose the soil particulates pollutants it has picked up. Their speed also erodes streambanks and soil surface. New locations of standing water can drown tree roots, too.

Wood thrush bird in a tree
Rock Creek Park provides critical nesting habitat for the wood thrush, DC’s bird.NPS Photo

Wood Thrush Migration

The wood thrush is the official bird of Washington, DC, and can be found in Rock Creek Park, but changes in climate may eliminate their regional population within the century. In addition to altering this songbird’s DC habitat and food sources, climate change negatively interferes with the wood thrush’s lengthy migration from Central America.

Wood thrushes fly up from the tropical forests of Central America every summer to their northern breeding grounds, anywhere from Florida to Maine. They need dependable ripe fruit and insect populations to fuel their journey, which may not be available as the climate warms. Furthermore, their usual breeding grounds are growing warmer, meaning they lose habitable areas and must fly farther north.

Animals and habitats: our allies in fighting climate change 

Thankfully, we have a powerful ally in our fight against climate change: animals and the ecosystems they are part of. The United Nations estimates that healthy ecosystems could account for 37% of the carbon reductions needed to limit global temperature rise.  

Healthy ecosystems with abundant plants and trees absorb carbon from the atmosphere and store it. So, preserving or restoring nature is a powerful tool in the race to stop climate change. Healthy ecosystems also filter water, buffer against flooding, reduce the impact of disasters, improve soil health and support rich biodiversity. Keystone species and nearly all animals play vital, sometimes invisible, roles in securing biodiversity and conserving habitats. 

For example, whales play a significant role in supporting healthy marine ecosystems. Whale poop provides nutrients to phytoplankton. Like plants, phytoplankton capture large amounts of CO2 and convert it to energy, removing carbon from the atmosphere. When phytoplankton are eaten by other marine animals, such as whales, the carbon continues to pass through the food web, remaining out of the atmosphere and not contributing to global warming. 

Elephants play important roles in engineering healthy ecosystems that in turn absorb CO2 and keep it out of the atmosphere. Elephants disperse seeds, fertilize soil, dig wells, create trails for other animals and clear space that encourages new plant growth. 

Pangolins eat ants and termites, keeping those populations regulated, and excavate dens that are used by other animals, both of which are essential in the ecosystems where pangolins live. 

Many other animals play equally important roles in the ecosystems where they live. 

Animals are changing their body shapes to cope with climate change

Global warming is a big challenge for warm-blooded animals, which must maintain a constant internal body temperature. As anyone who’s experienced heatstroke can tell you, our bodies become severely stressed when we overheat.

Animals are dealing with global warming in various ways. Some move to cooler areas, such as closer to the poles or to higher ground. Some change the timing of key life events such as breeding and migration, so they take place at cooler times. And others evolve to change their body size to cool down more quickly.

Our new research examined another way animal species cope with climate change: by changing the size of their ears, tails, beaks and other appendages. We reviewed the published literature and found examples of animals increasing appendage size in parallel with climate change and associated temperature increases.

In doing so, we identified multiple examples of animals that are most likely “shape-shifters” – including species in Australia. The pattern is widespread, and suggests climate warming may result in fundamental changes to animal form.

Adhering to Allen’s rule

It’s well known that animals use their appendages to regulate their internal temperature. African elephants, for example, pump warm blood to their large ears, which they then flap to disperse heat. The beaks of birds perform a similar function – blood flow can be diverted to the bill when the bird is hot. This heat-dispersing function is depicted in the thermal image of a king parrot below, which shows the beak is warmer than the rest of the body.

All this means there are advantages to bigger appendages in warmer environments. In fact, as far back as the 1870s, American zoologist Joel Allen noted in colder climates, warm-blooded animals – also known as endotherms – tended to have smaller appendages while those in warmer climates tend to have larger ones.

This pattern became known as Allen’s rule, which has since been supported by studies of birds and mammals.

Biological patterns such as Allen’s rule can also help make predictions about how animals will evolve as the climate warms. Our research set out to find examples of animal shape-shifting over the past century, consistent with climatic warming and Allen’s rule.

Thermal image of a king parrot, showing that the beak is warmer than the rest of the body. Image: Alexandra McQueen

Which animals are changing?

We found most documented examples of shape-shifting involve birds – specifically, increases in beak size.

This includes several species of Australian parrots. Studies show the beak size of gang-gang cockatoos and red-rumped parrots has increased by between 4% and 10% since since 1871.

Mammal appendages are also increasing in size. For example, in the masked shrew, tail and leg length have increased significantly since 1950. And in the great roundleaf bat, wing size increased by 1.64% over the same period.

The variety of examples indicates shape-shifting is happening in different types of appendages and in a variety of animals, in many parts of the world. But more studies are needed to determine which kinds of animals are most affected.

Other uses of appendages

Of course, animal appendages have uses far beyond regulating body temperature. This means scientists have sometimes focused on other reasons that might explain changes in animal body shape.

For example, studies have shown the average beak size of the Galapagos medium ground finch has changed over time in response to seed size, which is in turn influenced by rainfall. Our research examined previously collected data to determine if temperature also influenced changes in beak size of these finches.

These data do demonstrate rainfall (and, by extension, seed size) determines beak size. After drier summers, survival of small-beaked birds was reduced.

But we found clear evidence that birds with smaller beaks are also less likely to survive hotter summers. This effect on survival was stronger than that observed with rainfall. This tells us the role of temperature may be as important as other uses of appendages, such as feeding, in driving changes in appendage size.

Our research also suggests we can make some predictions about which species are most likely to change appendage size in response to increasing temperatures – namely, those that adhere to Allen’s rule.

These include (with some caveats) starlings, song sparrows, and a host of seabirds and small mammals, such as South American gracile opossums.

Why does shape-shifting matter?

Our research contributes to scientific understanding of how wildlife will respond to climate change. Apart from improving our capacity to predict the impacts of climate change, this will enable us to identify which species are most vulnerable and require conservation priority.

While our research shows some animals are adapting to climate change, many will not. For example, some birds may have to maintain a particular diet which means they cannot change their beak shape. Other animals may simply not be able to evolve in time.

So while predicting how wildlife will respond to climate change is important, the best way to protect species into the future is to dramatically reduce greenhouse gas emissions and prevent as much global warming as possible.

Climate change leads to a loss of species

Our planet is warming faster than at any time in the past 10,000 years. With these changes, species have to adapt to new climate patterns (variations in rainfall; longer, warmer summers etc).

Global warming resulting from human emissions of greenhouse gases. The consequences include habitat loss; shifts in climatic conditions and in habitats that surpass migrational capabilities; altered competitive relationships.

Changes already underway

Evidence suggests that the warming of the past century already has resulted in marked ecological changes, including changes in growing seasons, species ranges, and patterns of seasonal breeding.

Growing need for adaptations

The fate of many species in a rapidly warming world will likely depend on their ability to migrate away from increasingly less favorable climatic conditions to new areas that meet their physical, biological, and climatic needs.

Selection of the fastest?

WWF scientists have estimated that most species on this planet (including plants) will have to “move” faster than 1,000 metres per year if they are to keep within the climate zone which they need for survival.

Many species will not be able to redistribute themselves fast enough to keep up with the coming changes.

These species, as far as we know given present knowledge, may well become extinct.

Resources, “WHAT IS BIODIVERSITY?”;, “Wildlife and Climate Change: Catoctin Mountain ParkRock Creek Park.”;, “the impact of climate change on our planet’s animals.”;, “Animals are changing their body shapes to cope with climate change.”;, “A growing need for species to adapt to a changing world.”;, “The Effects of Global Warming on Wildlife.” By Earth Talk;, “Climate Change Is Threatening Animals Far More Than Scientists First Thought.” By Joe McCarthy;



-Global warming has the potential to cause extinctions in a majority of the world’s especially valuable ecosystems.

-Depending on a species responses to the warming, especially their ability to migrate to new sites, habitat change in many ecoregions has the potential to result in catastrophic species loss.

-Global warming is likely to have a winnowing effect on ecosystems, filtering out species that are not highly mobile and favouring a less diverse, more “weedy” vegetation and ecosystems that are dominated by pioneer species, invasive species.

Which Animals Are Hardest Hit by Global Warming?

According to Defenders of Wildlife, some of the wildlife species hardest hit by global warming include caribou (reindeer), arctic foxes, toads, polar bears, penguins, gray wolves, tree swallows, painted turtles, and salmon. The group fears that unless we take decisive steps to reverse global warming, more and more species will join the list of wildlife populations pushed to the brink of extinction.