Authors:
Ewa Węgrzyn, Konrad Leniowski, and Iryna Miedviedieva, Faculty of Biology and Nature Protection

Climate change and its impact on the biosphere have been the subject of scientific research for decades. As early as the 1970s and 1980s, it was observed that atmospheric concentrations of carbon dioxide (CO₂) were rising due to the combustion of fossil fuels and deforestation. This trend intensified in subsequent decades, leading to accelerated global warming. The latest reports by the Intergovernmental Panel on Climate Change (IPCC) indicate that temperatures will continue to rise unless we significantly reduce greenhouse gas emissions.

Even a 1.5°C increase in global temperature compared to the pre-industrial era is already causing tangible changes in ecosystems, such as the poleward or uphill range shifts of many species. More drastic warming—2°C to 3°C—could trigger irreversible feedback loops, including further melting of permafrost and the release of methane, a potent greenhouse gas. The intensification of extreme weather events (droughts, floods, hurricanes) and rising sea levels lead to habitat loss for many species and a decline in biological diversity.

Biodiversity, defined as the genetic, species, and ecosystem variety, forms the foundation of stable and resilient ecosystems. This stems from the fact that each species fulfills a specific role in its environment; the interdependencies among organisms—predators, herbivores, plants, saprophytes, and others—shape the persistence of natural systems. The loss of species disrupts food chains and has unforeseen consequences for the entire trophic network. Rising temperatures drive dynamic changes in habitats, leaving some organisms unable to adapt quickly enough to the new conditions.

Moreover, the current rate of climate change is faster than anything recorded in human evolutionary history. While past geological epochs did experience intense warming periods, those often spanned thousands or even tens of thousands of years, giving most organisms time to gradually adapt. Today, however, greenhouse gas concentrations are increasing at an incomparably faster rate—within a century or even a single human generation. As a result, many species are falling victim to these rapid changes, unable to adapt quickly enough.

An equally fundamental problem is the synergistic effect of climate warming and other anthropogenic factors: environmental pollution, urbanization, intensive agriculture, habitat fragmentation, the introduction of invasive species, and overexploitation of resources. All these phenomena collectively accelerate the extinction of animal and plant species, making the decline in biodiversity difficult to halt. Scientists now unanimously agree that we are living through one of the most intense episodes of mass extinction in Earth’s history—often referred to as the sixth mass extinction.

Climate Warming and Its Causes

Although natural climate cycles have always occurred on Earth, the current warming trend cannot be explained by natural factors alone. Greenhouse gases—primarily carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and industrial gases (e.g., CFCs)—play a crucial role here. Their high atmospheric concentrations trap heat that would normally radiate back into space. The greenhouse effect as a phenomenon is natural and essential for maintaining life on Earth—without it, the average temperature on the planet’s surface would be significantly lower. The problem, however, is the rapid rise in the concentrations of these gases due to human activities.

The main causes of increasing greenhouse gas emissions include:

1. Fossil fuel combustion – Coal, oil, and natural gas are the primary energy sources in the global economy. Their widespread use in transportation, industry, and power generation results in the emission of large amounts of CO₂.
2. Deforestation and ecosystem degradation – Forests, especially tropical ones, serve as massive carbon storage units. Their destruction (e.g., by burning land for agriculture) releases stored carbon into the atmosphere and reduces the planet’s capacity to sequester CO₂.
3. Intensive agriculture – Livestock farming, particularly of ruminants, produces high methane emissions. Overuse of synthetic fertilizers also generates nitrous oxide emissions.
4. Industry – Many industries (chemical, cement, etc.) rely on the combustion of large quantities of fossil fuels or use processes that release additional greenhouse gases.

Rising global temperatures due to the accumulation of greenhouse gases in the atmosphere have numerous consequences for ecosystems and their inhabitants. One of the most evident signs of these changes is the melting of mountain glaciers and polar ice sheets, causing sea levels to rise. Additionally, as CO₂ concentrations in the atmosphere increase, more of it is absorbed by the oceans, leading to lower seawater pH—a phenomenon known as ocean acidification.

Climate warming also correlates with more frequent extreme weather events. Droughts, heatwaves, floods, severe storms, and hurricanes can destroy habitats and drastically reduce the populations of local species. Furthermore, higher temperatures affect organisms’ biology—for instance, by disrupting developmental cycles, shifting breeding seasons, and altering food and water availability.

Mechanisms by Which Climate Warming Affects Ecosystems and Animals

Climate warming triggers numerous complex effects that directly or indirectly influence animal populations. Here are the most important ones:

1. Habitat Loss

One of the most critical factors driving species extinction is the shrinking of their natural habitats. Rising sea levels inundate coastal areas, wetlands, and river deltas. Many bird, mammal, and reptile species are then forced to migrate inland, where they may face competition from already established species. The reduction of sea ice in the Arctic means species like the polar bear lose their hunting platform and breeding grounds. Equally important are changes in mountain ecosystems, where certain species adapted to cold, high-elevation conditions (e.g., the American pika) find themselves caught between the too-warm valleys below and the receding ice or permafrost line above.

1. Changes in Food Availability and Trophic Networks

Rising temperatures affect the life cycles of plants and animals. For example, an earlier arrival of spring can disrupt the synchronization between plant development and the breeding period of insectivorous birds, leading to food shortages for their chicks. Similarly, in marine environments, warming can alter the phenology of phytoplankton and zooplankton—organisms crucial to the oceanic food chain. If plankton emerges at different times than before, some fish species may struggle to find food during critical developmental stages. This, in turn, affects predators that feed on these fish.

1. Thermal Stress and Disease

For species adapted to a narrow temperature range (so-called stenothermic species), even a small increase in ambient temperature can lead to metabolic disorders and thermal stress. Aquatic organisms such as riverine or mountain-stream fish are particularly sensitive to changes in water temperature. Moreover, higher temperatures promote the spread of pathogens and disease vectors (e.g., mosquitoes that carry viruses and parasites), resulting in higher infection rates and mortality among animals. This is not limited to tropical zones—diseases previously unknown in higher latitudes, such as dengue or the Zika virus, are starting to appear there.

1. Ocean Acidification and Degradation of Marine Ecosystems

The oceans absorb about one-quarter of the carbon dioxide emitted into the atmosphere. This leads to chemical reactions forming carbonic acid (H₂CO₃), subsequently lowering seawater pH. Ocean acidification is particularly dangerous for organisms that build calcium carbonate (CaCO₃) skeletons (corals, clams, marine snails, and some plankton species). In these organisms, calcification—essential for shell or skeleton formation—becomes more difficult. The result can be large-scale coral bleaching, which leads to the collapse of the diverse coral reef ecosystem.

1. Species Range Shifts and “Invasion” Phenomena

As climate conditions change, many species attempt to migrate to more suitable environments. This applies to birds, mammals, fish, and even plants, whose seeds can be carried by wind or water. While in some cases such movements represent natural range shifts, there is also the risk that in new habitats these species may become invasive, outcompeting local organisms and modifying the ecosystem. These shifts can have profound repercussions for local food chains and may hasten the extinction of some native populations.

Examples of Species Threatened by Climate Warming

1. Polar Bear (Ursus maritimus)

The polar bear is one of the most recognizable symbols of climate change. It inhabits Arctic regions, relying primarily on sea ice to hunt seals. The melting of Arctic sea ice significantly shortens the period during which polar bears can effectively forage. Increasingly, bears are observed traveling long distances in search of ice or resorting to land-based feeding, where they compete with brown bears, among others. Disrupted feeding cycles result in fewer offspring and a decline in the overall health of the population. Moreover, a shorter hunting season leads to hunger and weight loss, and in extreme cases—starvation. According to IPCC projections, continued warming will result in even faster melting of sea ice, jeopardizing the future of this species.

1. American Pika (Ochotona princeps)

The American pika, a small mammal related to rabbits and hares, lives in high-elevation areas of North America. It is adapted to cold climates and does not tolerate high temperatures. Once ambient temperatures exceed about 25°C, pikas are at risk of overheating, limiting their foraging activities. As the climate warms, their range shifts further uphill. Eventually, however, there are no higher elevations left, making it impossible to escape to cooler habitats. Local extinctions of pikas have already been observed in areas where temperatures exceed this species’ tolerance threshold. The loss of pikas can impact mountain ecosystems, as they contribute to soil aeration and serve as a food source for predators.

1. Reef-Building Corals

Coral reefs are often called the “rainforests of the sea,” acting as hotspots of marine biodiversity. Reef-building corals (Scleractinia) have a very narrow temperature tolerance range. A modest 1–2°C increase above the seasonal norm can trigger coral bleaching, whereby corals expel their symbiotic algae (zooxanthellae) that provide essential nutrients. Without algae, corals lose their color and become vulnerable to disease and death. Large-scale bleaching events have already been observed worldwide, including on the Great Barrier Reef off the coast of Australia. Ongoing ocean warming, combined with acidification, poses a serious threat to these vital ecosystems. The destruction of reefs results in the loss of habitats for thousands of other species, leading to a significant decline in marine biodiversity.

1. Amphibians

Amphibians are among the most endangered groups of vertebrates globally; drastic declines in their populations have been noted on various continents since the 1980s. Causes include disease (particularly chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis), habitat loss, and environmental pollution. Climate warming exacerbates these issues in multiple ways. Rising temperatures may favor the spread of pathogenic fungi; in drought conditions, amphibians lose moist refuges and breeding waters. Amphibians of the genus Atelopus in South and Central America rank among the fastest-disappearing amphibians, with many species already on the brink of extinction. Amphibians play a crucial role in freshwater ecosystems, controlling insect populations and serving as prey for other animals; their decline will thus have far-reaching consequences for entire biocenoses.

1. Sea Turtles

Many sea turtle species (e.g., the green turtle, loggerhead turtle, and leatherback turtle) are impacted by climate change at different life stages. Rising temperatures on nesting beaches affect the sex ratio of hatchlings because in reptiles, sex often depends on incubation temperature (generally, higher temperatures favor the development of females). Consequently, populations may become female-biased, eventually compromising genetic diversity. In addition, rising sea levels erode nesting beaches, and more frequent extreme weather events (e.g., hurricanes) destroy nests. In marine environments, turtles also suffer from pollution and ocean acidification, which disrupt food chains and food availability.

1. Adélie Penguins (Pygoscelis adeliae)

Adélie penguins inhabit Antarctica, and their life cycle is closely linked to sea ice conditions and the availability of Antarctic krill, a crucial component of their diet. Climate change affects the thickness and extent of sea ice, which in turn impacts krill populations. If sea ice melts earlier than usual, penguin colonies may have difficulty accessing food during the breeding season. At the same time, chicks become vulnerable to thermal stress when there is insufficient ice coverage and air temperatures fluctuate wildly. Although some Adélie penguin populations adapt by changing their breeding grounds, many colonies are experiencing significant declines.

Why Climate Warming Contributes to Species Extinction

The mechanisms driving the extinction of animal populations are multidimensional and interlocking. Several main factors explain why climate warming accelerates the decline of species:

1. Excessively Rapid Pace of Change – While species have evolved under changing climates, today’s scale and speed of warming far exceed many organisms’ natural adaptive capacity.
2. Habitat Fragmentation and Loss – Species that cannot easily migrate or adapt to new conditions experience drastic population declines.
3. Disruptions in Trophic Networks – Temporal (phenological) and spatial (geographical) shifts disturb predator-prey and plant-pollinator relationships, reducing feeding and reproductive success.
4. Increased Disease and Parasite Pressure – Warmer climates allow pathogens to spread into new regions and hosts, leading to mass disease outbreaks.
5. Cumulative Stressors – Global warming acts synergistically with other threats, such as pollution, overharvesting, agricultural expansion, and urbanization.

Consequently, species with already limited ranges, narrow habitat preferences, or high sensitivity to environmental changes are the most vulnerable to extinction.

Mitigation Measures and Future Prospects

1. Reducing Greenhouse Gas Emissions

The primary and most effective way to combat climate warming is by lowering greenhouse gas emissions. Actions in this area include:

• Transitioning the energy sector toward renewable energy sources (RES) such as solar, wind, hydro, or geothermal power.
• Increasing energy efficiency in buildings, transportation, and industry.
• Changing agricultural practices to reduce methane emissions from livestock farming, alongside reducing meat consumption and food waste.
• Reforestation and forest conservation—promoting strategies that protect natural ecosystems, which absorb and store carbon dioxide.

Multilateral agreements like the 2015 Paris Agreement set emission reduction targets and aim to limit the temperature increase. However, to keep warming below 2°C (preferably 1.5°C) relative to the pre-industrial era, urgent and profound changes in the global economy and lifestyles are necessary.

1. Habitat Protection and Ecological Corridors

Since habitat transformation is a major driver of species extinction, nature conservation efforts should include:

• Establishing reserves and protected areas in regions crucial for biodiversity conservation.
• Restoring degraded ecosystems, such as wetlands, forests, and coral reefs.
• Creating ecological corridors that enable species to migrate in response to shifting climate conditions.
• Avoiding excessive urbanization and habitat fragmentation in favor of sustainable spatial development.

Examples of such efforts include wetland restoration projects in Europe and the creation of wildlife corridors in the United States. Similarly, in marine areas, establishing networks of protected zones helps safeguard coral ecosystems and supports their recovery.

1. Monitoring and Scientific Research

Accurate scientific data on animal population status, climate trends, and ecosystem changes are essential for effective decision-making. The advancement of remote sensing and environmental modeling methods is crucial. Monitoring programs (e.g., the Global Biodiversity Information Facility – GBIF) collect data from around the world, enabling trend analyses and forecasting. International cooperation, research funding, and knowledge exchange between scientists and policymakers form the basis for sound climate and conservation policies.

1. Species Reintroduction and Ex Situ Conservation

In some cases, when populations are extremely threatened, reintroduction is used—releasing individuals bred in conservation facilities (e.g., zoos or specialized centers) back into the wild. Such actions carry risks (e.g., lack of adaptation to natural conditions, potential impact on local populations), but they can help prevent a species’ total disappearance. Ex situ conservation also involves seed banks and the preservation of animal tissues and cells, which could be used to rebuild populations in the future—if environmental conditions allow.

1. Education and Public Engagement

Understanding the causes and impacts of climate warming, as well as the importance of biodiversity, is key to implementing real changes. Environmental education in schools, public awareness campaigns, and media engagement can help people appreciate why nature conservation is not a luxury but a necessity. Public support and conscious consumer choices (e.g., reducing carbon footprints, purchasing eco-certified products) can pressure governments and businesses to take more effective measures. Increasingly, grassroots movements, youth initiatives, and environmental organizations are demanding urgent action in the political and economic spheres.

Summary and Conclusions

Global warming represents one of the most serious contemporary threats to biological diversity, and its negative effects are already evident across various ecosystems worldwide—from the Arctic to the tropics. The mechanisms driving animal extinction include habitat loss, trophic network disruptions, thermal stress, the spread of diseases and parasites, and the synergistic impact of other human-driven pressures. Examples of species such as the polar bear, American pika, reef-building corals, amphibians, and sea turtles illustrate the scale of the challenges in both terrestrial and marine ecosystems.

Halting biodiversity loss requires comprehensive measures to reduce greenhouse gas emissions, protect key natural areas, and enable species to adapt to rapidly changing conditions. International initiatives (such as the Paris Agreement) are important, but so are local, grassroots conservation projects and sustainable economic practices. Long-term success depends on combining efforts at governmental, scientific, private, and societal levels.

In the coming decades, we will have to contend with further climate warming. Even the most optimistic scenarios predict continued temperature increases, although there is a chance to stabilize them if we quickly and decisively cut greenhouse gas emissions. Ecosystem adaptation will hinge on the ability of individual species to migrate or adapt to new conditions, as well as on preserving sufficiently large natural areas connected by corridors.

Preventing species extinction in the face of climate change is not only an ethical or environmental imperative but also a requirement for maintaining stable ecosystems upon which humanity depends. The economic benefits of ecosystem services (pollination, clean water, air purification, soil stability, etc.) are invaluable, and their loss could have long-lasting negative economic and social repercussions.

Ultimately, the fate of many species—including potentially our own—depends on whether we recognize the seriousness of the situation in time and implement large-scale global actions. Collective efforts to reduce emissions, manage natural resources sustainably, and promote education can still avert the worst-case scenarios. Preserving biological diversity is essential for maintaining life on Earth as we know it, and combating climate warming is a cornerstone of that conservation effort.