Life on Earth is diverse at many levels, meaning there is a lot of variety within species and there are many different kinds of species. This biodiversity provides many of the resources that humans need and enhances our quality of life. All of Earth’s organisms are affected by Earth’s climate, but they also influence Earth’s climate. In this article, we show how research on plants, animals, and microbes helps us better understand how living things can both impact and respond to climate change. This research also gives us insight into what the future might be like for life on Earth. Such knowledge will help us to protect our planet—and the living things on it—from the harmful effects of future climate change.
What Is Biodiversity?
Many different kinds of microbes, plants, and animals (including people) live on Earth. Collectively, all these different organisms make up Earth’s biodiversity. Biodiversity includes genetic diversity among individuals and among populations within species. Biodiversity also includes diversity of species, and communities of species within ecosystems. Biodiversity provides humans with many important resources, such as a variety of nutritious foods, and recreational activities. In addition, biodiversity can be important for cultural reasons, including national identity and religious ceremonies. Biodiversity also holds the potential for undiscovered benefits, like potential new medicines and protection of agriculture and livestock from disease outbreaks. For all these reasons, we must try to understand and protect Earth’s biodiversity.
How Can Living Things Contribute to Climate?
Living things are clearly dependent on their environment, but they also affect their environment—even on a global scale. Organisms can affect the global climate because of their huge numbers. For example, the majority of carbon dioxide (CO2) in the air is eventually consumed through rock weathering into dissolved river nutrients (Figure 1). However, the enormous numbers of plants and microbes on Earth collectively control the amount of CO2 that remains in the air because they take it up to build their bodies. This is important for climate because CO2 traps heat in the Earth’s atmosphere, which, through the greenhouse effect, contributes to global warming.
According to the International Union for Conservation of Nature (IUCN)1, the world’s forests absorb about one-third of the CO2 that is released from burning fossil fuels (like gas, oil, and coal). In addition, the Global Carbon Project2 reported that a quarter of the CO2 released from burning fossil fuels is quickly absorbed by the oceans. There, ocean microorganisms take up CO2 and use it to build their cells.
The vast majority of carbon captured by organisms is released again to the air in a few years when organisms die. However, a small fraction of their carbon is deposited in the soil or ocean sediments. This removal of carbon from the environment is largely balanced out by volcanic processes. After hundreds of millions of years, the carbon returns to the air as CO2 when volcanoes erupt, completing the natural carbon cycle (Figure 1). Atmospheric CO2 has increased dramatically because many human activities rely on burning fossil fuels. Burning releases the carbon back into the atmosphere as CO2 3. Currently, human activities release nearly 100 times more CO2 into the atmosphere than volcanoes do .
Humans must therefore be part of the solution to climate change. We can stop burning fossil fuels and cutting down forests. Actively replanting forests and restoring or preserving other natural systems that store a lot of carbon (like peatlands) are also important to combat climate change. Scientists think that if oceans become warmer, there will be fewer carbon-removing microorganisms (Figure 1 insert). This would leave more CO2 in the atmosphere. Preventing global warming will help protect the ocean’s microorganisms, and thus help to stop climate change.
How Does Climate Affect Biodiversity?
Not only does life affect the climate, but climate also affects life . As Earth’s climate changes, some individuals that can tolerate the new conditions might survive and reproduce, passing on their tolerant traits, while others will die. This process is called evolution. Some organisms migrate to follow the conditions that are right for them. Animals might move because temperatures get too high, or because food sources become scarce. But not all species can move. For example, organisms in polar regions or at the tops of mountains are already living in the coldest places on Earth. When climate changes quickly, many species cannot adjust quickly enough, and become extinct . The interactions of organisms with their environments can thus affect the Earth’s biodiversity in many ways.
Changes in one species affects other species within the same community. Long-term studies of the interactions between species are important for predicting the future of life on Earth. For example, scientists have studied Edith’s checkerspot butterfly for over 70 years (Figure 2). At one site, the success of the butterfly was dependent on one plant species (blue-eyed Mary). Then cattle ranchers brought in a new plant (plantain). Edith’s checkerspot completely switched to using plantain. When cattle were taken off the land, the plant community changed again, and this time the butterfly population died off completely. Sometimes humans change things in the environment too fast for populations to adjust4. This can happen if there are not enough individuals in the population that can tolerate the new conditions.
Corals are another important example. These animals build their skeletons with a substance called calcium carbonate (CaCO3), forming reefs like the Great Barrier Reef of Australia. Reef formation depends on the amount of CO2 in the atmosphere because that influences how much CO2 is taken up by the ocean. CO2 reacts with ocean water to form carbonic acid, which makes the ocean more acidic5. When ocean water is acidic, it reduces the growth and survival of corals. Coral reefs are important ecosystems—they provide breeding grounds for fish and hiding spots for other marine life. Without reefs, marine communities become less stable and collapse .
Marine habitats are also experiencing rapid changes in salt content. Rainfall patterns are changing around the world, and polar ice is melting rapidly. Oceans near the poles are becoming less salty, while the oceans closer to the equator are getting saltier. These rapid changes put enormous stress on marine organisms because salt levels must be maintained for proper function. Some populations can evolve in the saltier conditions, but others will die off. Species that do not live very long can evolve faster. For example, some copepods (small crustaceans) live only a few weeks and the average salt tolerance of the population can increase in just a few years. However, longer-lived plants and animals take much longer to evolve. This is true for many populations of fish which may decline in numbers or die off completely due to changes in salinity.
Changing climate conditions may also allow non-native species to thrive and become invasive. This is partly because native species may become stressed by the changing climate conditions. Invasive species may be more tolerant of the new conditions and may even grow more aggressively in the invaded areas than in their native areas! One example is Japanese knotweed. This plant tolerates many disturbed and stressful habitats, and has taken over in many areas around the world6.
How Do We Predict How Organisms Will Respond to Climate Change?
Scientists study how organisms are changing in natural conditions and under experimental conditions. For over 100 years, studies of organisms in their natural conditions have shown changes in the life cycles and distributions of many plants, animals, and microbes in oceans, lakes, rivers, and on land as a result of climate change . Warmer winters and springs have caused plants to flower earlier, trees to grow leaves earlier, and birds and butterflies to migrate earlier. Many plants and animals have moved closer to the poles and higher into the mountains as they try to keep pace with the changing climate (Figure 2).
It is hard to predict what will happen to living things when the Earth gets even hotter. One way is to take a closer look at corals because they provide an important window into the climate of the past (Figure 3). Corals grow slowly, and they incorporate the chemistry of the surrounding ocean into their skeletons. Scientists can “read” this information and use it to reconstruct the past living conditions of the corals. Some corals are 500 years old, giving us the chemical history of the last 500 years almost month by month!
Scientists also study fossils from the distant past. Over great spans of time, plants, animals, and microorganisms have been forced to respond to very large climate changes. Sometimes, the changes were similar in size to changes we will see in future climates. In the fossil record, we can see what happened to life when the climate changed dramatically . During major changes in Earth’s past climate, many species migrated to more comfortable locations, some species became extinct, and a very few managed to stay in place and adapt to the new climate.
How Can Biodiversity Help Us Understand the Future?
As far as we know, the diversity of life seen on Earth is unique in the universe. This diversity has provided humans with many of the things we need to survive. Plants and microbes on land and in the oceans, produce the oxygen that all animals (including humans) need to breathe. Ocean fisheries provide food and jobs for many people. Reefs, marshes, and mangroves protect our coasts. Forests provide us with wood to build things, and our croplands give us food. In addition, living things remove CO2 from the atmosphere and the oceans. Without them, temperatures would be much hotter. Living things are also affected by the changing environment. Climate affects the availability of resources and the chemistry of the oceans. By studying many different types of life and many different environments, we hope to understand how life will respond to—and affect—future climate change.
The authors are all part of the Franco-German Make Our Planet Great Again program (https://makeourplanetgreatagain-cnrs.com/ and https://tinyurl.com/mopga-gri) which in part supported research on the interactions between life and climate.
Biodiversity: ↑ The variety of life (plants, animals, and microorganisms) measured at within a certain species, ecosystem or on Earth.
Evolution: ↑ The changes in traits passed down through generations of organisms. Some traits, or adaptations, help individuals survive and succeed in their unique environments.
Coral: ↑ 1: A tiny soft-bodied animal. Corals live in colonies and build a stony skeleton. 2: A piece of stony material which is the skeleton of corals.
Invasive Species: ↑ Organisms that are transported to a new location where they had previously not existed but then begin to change or threaten the local communities.
Conflict of Interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
1. ↑The International Union for Conservation of Nature (IUCN; https://www.iucn.org) is like the Intergovernmental Panel on Climate Change (IPCC), but with a specific focus on conservation of diversity. Like IPCC, it is funded by ~200 governments and civil society organizations, policy is built through intergovernmental studies and is government approved.
4. ↑See the story of Edith’s checkerspot on Youtube: The tale of the Edith’s checkerspot: Butterflies caught in an evolutionary trap.
5. ↑To learn more about the effects of ocean acidification, see the short animation about the potential impact on sea life in the Gulf of Maine A Climate Calamity in the Gulf of Maine Part 2: Acid in the Gulf.
 ↑ Masson-Delmotte, V., Zhai, P., Pirani, A., Connors, S. L., Péan, C., Berger, S., editors, et al. IPCC, 2021: Summary for Policymakers. Climate Change 2021: The Physical Science Basis Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. Available online at: https://www.ipcc.ch/report/ar6/wg1/
 ↑ Parmesan, C. 2006. Ecological and evolutionary responses to recent climate change. Annu. Rev. Ecol. Evol. Syst. 37:637–69. doi: 10.1146/annurev.ecolsys.37.091305.110100
 ↑ Trubovitz, S., Lazarus, D., Renaudie, J., and Noble, P. J. 2020. Marine plankton show threshold extinction response to Neogene climate change. Nat. Commun. 11:5069. doi: 10.1038/s41467-020-18879-7
 ↑ Parmesan, C. 1996. Climate and species’ range. Nature. 382:765–6. doi: 10.1038/382765a0
 ↑ Pandolfi, J. M., Connolly, S. R., Marshall, D. J., and Cohen, A. L. 2011. Projecting coral reef futures under global warming and ocean acidification. Science. 333:418–22. doi: 10.1126/science.1204794