How Are Plants and Animals Responding to Climate Change?

Major shifts have been observed in species distribution, range boundaries, migration patterns, and phenology as a consequence of climate change. These changes have diverse implications for biodiversity and humanity.

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Climate change and other human-driven environmental impacts are altering ecosystems and affecting the lives of millions of plant and animal species.

The Earth has warmed 1.3C since 1850, primarily due to human-generated greenhouse gas emissions. The temperature increase has contributed to accelerating climate effects including drought, heat, sea level rise and wildfires.

Drought

Nearly 25% of the global population experienced drought conditions in 2022 and 2023. The latter was also the driest year in three decades for the world’s rivers. Drought is projected to become more frequent in the future, with the severity ranging from 33% to 62% of global land area under a low or high emission scenario.

Heat

The ten hottest years on record all occurred in the last decade, with 2024 topping the ranking. Climate change contributed to 41 additional days of extreme heat in 2024. Extreme heat increases ecosystem vulnerability, wildfire and drought risk, fuels more powerful hurricanes and contributes to sea level rise.

Sea level rise

Global sea level has risen 8-9 inches (20.3-22.9cm) since 1880 and reached an all-time high of 10.14 centimeters above 1993 levels (first year of satellite record) in 2023. Sea level rise is driven primarily by melting of the earth’s mountain glaciers and polar ice sheets. Glacial, arctic and Antarctic melting has accelerated each decade.

Sea level rise is projected to reach 1 foot (30.5cm) above 2000 levels by 2100 in the most optimistic scenario aligned with the Paris Climate Agreement target of 1.5C. The current trajectory of 3.1C of warming by 2100 means sea level rise may be closer to the high emission scenario of 6 feet or higher by 2100.

Wildfires

Wildfires are becoming more frequent, intense and widespread. Between 2001 and 2023, the area burned by fires increased by 5.4% per year, resulting in 6 million more hectares burned annually compared to 2001. The global fire season got 18.7% longer from 1979 to 2013. Hotter, drier conditions are contributing to more severe fires that release 50% more carbon per unit burned area than in the early 2000s.

How Are Human Activities Impacting Ecosystems?

Humans are altering ecosystems in ways that dramatically reduce the habitat and natural resources available to other species and contribute to climate change. 

Deforestation and land conversion for development and agriculture, for example, is removing over 18 million acres of forest habitat per year.

Meanwhile, global demand for water has contributed to the loss of 30% of freshwater ecosystems including rivers, lakes and wetlands, which together provide habitat for 10% of all species.

Widespread use of pesticides to eliminate insects and boost agricultural productivity can be toxic to other organisms and contaminate freshwater sources. A 2022 study of 92 active ingredients in pesticides and data mapping agricultural use in the US estimated that pesticide use on 33% of agricultural land in the US was at a level high enough to be considered a risk to ecosystems. Global pesticide use has grown by about 11% per year since the 1950s and totals over 3 billion kilograms annually.

Observed Changes in Plant and Animal Species

Distribution and migration

Plants and animals in terrestrial ecosystems are moving to cooler environments at higher latitudes in response to warming. Melting of the polar ice sheets has enabled the movement of marine species into new areas.

Declining sea ice is contracting the habitat ranges for animals that have successfully adapted to previous glacial retreat. The Adelie penguin is dependent on ice throughout its life cycle. The sea-ice season in the Arctic and Antarctic shortened between 1979 and 2010 due to rising temperatures. Penguins are shifting their breeding grounds further south and must travel further for food and breeding. Population declines of over 40% have been observed in the eastern Antarctic Adelie penguin populations.

Ocean warming and falling water acidity are causing corals to expel the symbiotic algae from their tissues resulting in a loss of color known as coral bleaching. Coral reefs are considered  keystone species in that they are critical for ecosystem balance and shelter 25% of all marine species. Coral reef systems have declined 14% since 2009 and a 2024 analysis indicated that 44% of the remaining 892 warm-water coral reef species are at risk of extinction due to projected future warming and other threats from human activities.

Phenology

Phenology refers to seasonal and cyclic expression in plant and animal species. The timing of these lifecycle events is influenced by changes in climate and weather patterns. Climate change is altering phenological processes, including flowering and emergence of larval insects such as caterpillars, with potential for global impacts.

Research supports an association between warming and early flowering. A 2022 study of first flowering dates of 406 plant species from before and after 1986 found an average shift of 26 days earlier in the year. This creates risk for temporal mismatch between earlier flowering plants and insect pollinators that generally adjust less quickly to warming. Temporal mismatch could have significant consequences for food systems as about 35% of global food crops depend on pollination to reproduce. Bee populations worldwide have already declined in recent decades due to habitat loss, pesticide use and air pollution.

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Range and population size

Warming temperatures favoring disease-carrying insects is a threat to public health worldwide.

Ticks are responsible for 95% of annual vector-borne diseases in the US, including Lyme disease and Rocky Mountain spotted fever. Historically, their range has been limited to the Northeast, Gulf Coast and Upper Midwest. However, warming has enabled expansion into southern Canada and the western US. Lyme disease is the most common vector-borne disease in the US, with a nearly 25 times increase of annually reported cases since 1982.

Climate change is also creating favorable conditions for mosquitos – the deadliest creature on Earth – to breed. Mosquito-borne diseases are responsible for more than one million deaths and 700 million infections per year. Warmer temperatures accelerate mosquito development and lengthen disease transmission seasons by a month or more. Extreme precipitation and flooding have increased in frequency and intensity since the 1950s and leave additional standing water ideal for mosquito breeding.

How Can Humans Support Species Adaptation to Climate Change?

The greenhouse gas emissions emitted by human activities have ensured that changes to species and ecosystems will continue into the distant future. According to the International Union for Conservation of Nature (IUCN), climate change is already directly impacting at least 10,967 species on the IUCN Red List of Threatened Species. 

The Earth is on pace for 3.1C of warming. If nothing is done, one-third of species worldwide could face extinction by the end of the century.

Two key strategies are assisted migration and protected areas.

Assisted migration

Assisted migration involves the relocation of plants or animals to more suitable habitats. The US Endangered Species Act was updated in 2023 to allow for this intervention as it was previously thought moving species was too potentially destructive to the destination habitat. However, the pace of climate change is exceeding species capacity to successfully adapt naturally.

Climate scientists with the US Forest Service are utilizing assisted migration to test replacement tree species for an area in Minnesota formerly containing ash trees that were destroyed by the emerald ash borer, a non-native invasive insect species. The test trees include species resilient to the emerald ash borer and those accustomed to warmer environments.

Assisted migration is also being considered by wildlife officials in Florida to save a dwindling population of deer. The key deer are native to the Florida Keys and their habitat is threatened by sea level rise and saltwater intrusion. Relocation to mainland Florida may be the last remaining option to save the 1,000 remaining in the wild.

Protected areas

Protected areas have long been utilized to preserve locations with cultural or natural values from human presence and exploitation. Considered the cornerstone of biodiversity conservation by the Convention on Biological Diversity, there are around 130,000 protected areas covering 13% of terrestrial surfaces and 6% of marine areas.In 2022, the UN Convention on Biological Diversity adopted the goal of achieving protection of at least 30% of global lands, inland waters, coastal areas and oceans by 2030. Studies have shown that when effectively managed, protected areas are effective at reducing habitat loss, preserving biodiversity and improving species conservation compared to those with no protections. Protected areas that limit deforestation and land clearing also contribute far less carbon emissions than unprotected forests.