Carbon dioxide is perhaps not the most potent of all the greenhouse gases, but due to its large proportions and long lifespan, it is the most significant climate change accelerator. Therefore it is necessary to learn about the carbon cycle in nature.

Carbon is constantly recycled and reused between the reservoirs (the atmosphere, oceans, plants, terrestrial ecosystems, sediments). For a long time, the oceans, terrestrial vegetation and soil have absorbed carbon dioxide from the atmosphere and represented so-called carbon sinks. However, scientists suggest that climate change weakens carbon sinks. When humans add carbon dioxide to the atmosphere, it is divided according to a carbon cycle between oceans, vegetation and the atmosphere. About 45% of CO2 has remained in the atmosphere, while about 30% has been taken up by the oceans and the last 25% has been taken up by the terrestrial biosphere.

During photosynthesis plants remove carbon dioxide from the atmosphere and act as carbon sinks. The bacteria and fungi use cellular respiration to extract the energy contained in the chemical bonds of the decomposing organic matter, and thus release carbon dioxide into the atmosphere.

Large amounts of carbon dioxide from the atmosphere dissolve in the surface waters of the oceans, but at the same time, much of it gets released into the atmosphere. However, single-cellular plankton keeps the carbon cycle going in the seas. Through photosynthesis, plankton consume carbon dioxide in the surface waters and once they die, they begin to sink and release carbon dioxide to the deep seawater and sediment. Since the sea floor is not in contact with the atmosphere, carbon dioxide cannot be released by it. This mechanism is known as the biological carbon pump and it explains why the oceans have such a big share of carbon.

Carbon cycles so rapidly that a single carbon dioxide molecule remains in the atmosphere only about five years. Most of the carbon dioxide absorbed by vegetation and the oceans is released back into the atmosphere quite soon. The atmospheric longevity of man-made carbon dioxide can be described as follows: if 100 new carbon dioxide molecules are added to the atmosphere, after 30 years, 50 extra CO2 molecules are retained. Due to a fast carbon cycle, most of the molecules are not the original ones. After a few hundred years, there are still 20 extra molecules left in the atmosphere and a small number of these emissions are adding carbon dioxide content into the atmosphere even for thousands of years until it ends up at the bottom of the ocean.

Because of climate change, land, plant and ocean carbon sinks are likely to become less effective. In a warming climate, soil organisms break down organic matter quicker and CO2 absorbed by plants is released more rapidly into the atmosphere. In addition, it is likely that in some areas climate change could lead to soil degradation and turn rainforests into savannahs, which have much lower carbon sequestration efficiency. In some other areas, e.g. tundras becoming forested, vegetation might be capable of increasing carbon dioxide capture. However, there are indications that, over time, this will become a less efficient sink of man-made carbon on a global scale. Thus, the weakening of carbon sinks would function as a negative feedback loop that drives climate change. (For further information, see the text on physics.) According to various studies, climate change will affect the carbon pumps of the oceans in such a way that they are unable to absorb CO2 as quickly as it is being emitted by human activities.

In addition to carbon dioxide, other greenhouse gases contribute to climate change in many ways and through different mechanisms. For example, methane is distinctly stronger than carbon dioxide, but considerably short-lived. It is generated by the fermentation of organic matter including swamps, rice fields and landfills. Methane lasts about twelve years in the atmosphere before it gets oxidized and turns into water and carbon dioxide.

The Earth is estimated to be about 4,6 billion years old and its climate has changed a lot throughout its history. According to current understanding, the Earth’s climate has had many warm periods and at least six millions-of-year long cycles of cold periods when most of the planet was covered in ice. During the cold periods, large ice sheets were formed close to either the South or North Pole or both. Currently, the Earth exists during the most recent glacial period, which started approximately 30 million years ago.

The Earth has had twelve major extinction events, out of which six have been identified as mass extinctions. There is still debate about the causes of these mass extinctions that took place hundreds of millions of years ago, but it is speculated that large extinctions may have resulted during rapid climate changes. Significant global warming of the seas and climate has accelerated at least on the first, second, fourth and the ongoing sixth mass extinction periods.

The species living outside their native distributional range are called introduced species. For example, the golden jackal of North Africa has expanded its range to Europe in the last 100 years and appears already as far north as Estonia. In Finland, for example, peacock butterfly populations have increased due to global warming. The difference between introduced species and invasive species is that invasive species arrive outside their native range without human assistance as a by-product of natural movement or traveling seeds.

If change exacerbates living conditions, species may try to adapt or relocate into more accommodating habitats either by migrating (animals) or spreading seeds (plants). Adaptation can mean either adapting a new type of behaviour or developing new physiological qualities. If change is happening too quickly for a particular species to adapt or find a new habitat, that species face local or even global extinction. Species at risk from climate change are, among others, the polar bear, the Saimaa ringed seal and the arctic fox. Species that evolve slowly in adapting to the rapid change are being hit hardest.

Changes in the biophysical environment have a wide-ranging impact on ecosystems. A decline or increase of a certain species in a certain area typically affects the other inhabitants. For example, increased numbers of pest populations pose a challenge to vegetation. Another example is the expansion of competing species in a certain area which may pose a threat to native species of that area. Red foxes are expelling arctic foxes due to the warming climate which allows them to survive much further north. This represents one example of this type of invasive competition. At the same time, better living conditions for animals that other animals typically prey upon increase the number of predators.

Climate change causes shifts in phenology; in other words, seasonal changes in plants and animals from year to year. In practice, this means that, for example, growing seasons have become longer in cool areas around the world. The northern hemisphere is already seeing the outbreak of spring with budding flowers and plants earlier than in past decades, and autumn is arriving later or lasts longer with plants withering later in the season.

One of the clearest examples of climate change in action is species moving towards the South and North Poles and to the mountainous areas towards the peaks. In addition, the rising sea level impacts migration and there are already signs of this in the fragile coastal areas, such as mangrove forests. So far, most studies on the consequences of the sea level rise have focused on local ecosystems, whereas large scale impacts on biodiversity have not been considered.

However, it is vital to keep in mind that predicting the impacts climate change will have on our natural environment is not straightforward since the impacts vary greatly across regions.

The changing climate impacts ecosystems in many ways. Global temperature increases might lead to longer growing seasons and therefore range shifts or habitat loss in some areas. This causes changes in food webs, which influence species and their populations. In addition, climate change is increasing heavy precipitation, droughts, extreme weather and forest fires. It is likely that thriving species and populations under future climates will differ genetically from those currently inhabiting the planet.

Climate change could drive thousands of species to extinction and put many more at risk within 100 years. According to some estimates, the situation may even be direr. However, it is difficult to point out whether climate change has caused some particular extinction of species. Extinctions may have many other primary factors, such as host and pollinator decline or increase in infectious diseases, although climate change might be the root cause. Currently, it is not known exactly which factors are the most crucial. Impacts of climate change might also become more severe if it drives other man-made environmental problems, such as habitat loss and fragmentation.

So far, there is very little evidence of global extinctions related to the changing climate. Studies suggest that the first mammal species that have gone extinct due to human-induced climate change is the species Melomys rubicola, a small rodent that lived exclusively on the Bramble Cay coral island in Australia. However, there is plenty of evidence of local extinctions. In response to global warming, the natural ranges of many species reduce and shift, which causes local extinctions. Range shifts have already been observed in hundreds of species. For example, the American pika in the United States, the turbellarian flatworm Crenobia alpina in Wales, and 48 lizard species in Mexico have experienced extinction tied to climate change.

At the moment the rate of global extinctions is increasing rapidly but most of the species likely to face extinction due to climate change are not currently even at risk. The most accurate predictive elements when identifying extinction risk are a small current geographic range and limited overlap between this and the species’ potential future range. In Finland, this concerns many endangered and particularly some native species.

Diverse, natural and functional ecosystems have the best chances to adapt to climate change. At the same time, climate change hits hardest species-rich and vulnerable ecosystems. For example, in the Arctic regions, due to global warming, coniferous forests may expand northwards into tundra. Climate change is faster and more severe in the Arctic since climate significantly regulates growth and reproduction of species. Related to this fact is that the Arctic Sea prevents species and habitats from moving towards the north. Therefore, the Arctic species are at serious risk.

The following changes have been estimated in the other vulnerable ecosystems:

• Deserts and dry ecosystems will expand.
• Steppes and savannahs will have competition between trees and grasses.
• Regions with Mediterranean forests, woodlands and scrub droughts will cause degradation of biodiversity.
• In forests, climate change will accelerate vegetation growth but also increase the risk of forest fires.
• The ice cover will disappear in the Arctic areas and they will gradually become forested while native species suffer.
• In mountainous regions, plants and animals will move to higher elevations.
• Swamps will dry out or be forested.
• Fresh water ecosystems will dry out and suffer from the impacts of eutrophication and their native species will shift towards the South and North Poles.
• Wetlands will become terrestrial ecosystems or their primary production will increase.
• Sea temperature rise will affect marine biodiversity and primary production in the oceans will decrease.
• Coral reefs and the protection they provide for marine species will rapidly disappear.
• Rising seas will drown coastal ecosystems, such as mangrove forests.

The current rate of ocean acidification is fast and it endangers the future of many sea creatures. Ocean acidification is caused by the uptake of excess carbon dioxide from the atmosphere, which in turn accelerates a decrease in the pH of the Earth’s oceans. Since the beginning of the Industrial Revolution, the surface ocean pH has decreased by 26%. Studies suggest that the current rate of ocean acidification is unprecedented – faster than at any time in the past 300 million years. It is estimated that if carbon dioxide levels continue to rise, acidification may increase 170% by the end of the century.

Acidification is happening at the fastest pace in the Arctic waters, and change is already so rapid that many species are not able to adapt. Change is also evident in the Pacific Ocean, where corals, molluscs and gastropods with calcium carbonate shells are at risk. The only solution is an immediate, large-scale cut of carbon dioxide emissions.

Deforestation is due to logging and is accelerated by large-scale forest fires around the world. Logging is done for wood processing, paper, the energy industry and agriculture. Deforestation occurs particularly in tropical rainforests. When trees are logged, they release the stored carbon back into the atmosphere since logged forests cease to function as carbon sinks. Deforestation adds more atmospheric CO2 than the sum total of all cars and trucks on the world’s roads.

Deforestation accelerates climate change and also contributes to the decrease of biodiversity by eliminating habitats of thousands of tropical species. The most effective way to tackle deforestation would be rainforest conservation, but also sustainable agriculture and forest management, as well as education, are needed to solve the problem.

Habitat fragmentation leads to the decrease of biodiversity. It causes major problems to many species and complicates adaptation to climate change due to stress. One way to improve adaptation is to reduce other stress factors, such as the above-mentioned strategies regarding habitat fragmentation. There is no all-inclusive solution to this problem, however, for example, implementing wildlife corridors can be helpful. Biodiversity conservation planning should also be based on the specific species habitat requirements.

Safeguarding and protecting the biodiversity of nature are the main goals of Finnish legislation on nature conservation. In Finland, conservation is mainly concentrated in nature reserves and wilderness areas covering some 9% of the country’s surface area. The aim is to protect species and natural habitats. While nature reserves do not and cannot cover them all, conservation is necessary since many species and habitats are endangered.

Species and their habitat ranges shift as a result of climate change, therefore nature reserves will not necessarily appear to be a guarantee for the future protection of species. When species shift towards the north, many endangered plants and animals may face extinction when moving their habitat is not an option. At the same time, the new habitats may be small, fragmented and in a need of conservation.

Even if many species would shift away from protected areas, reserves still play an important role in protecting different habitats. They provide habitats for new and vulnerable species to reproduce and reside. By increasing the size of the protected areas and in the process creating connections between them by implementing wildlife corridors or rehabilitating habitats, survival of endangered species can be improved greatly. Since species range shifts are not always dependent on geographical limits, conservation planning requires international cooperation. In addition, there is demand for new protected areas.

However, protected areas are not enough to guarantee the survival of a species. It is also important that the areas outside the nature reserves be managed in a sustainable manner. This concerns particularly forests and agricultural landscapes.

Conservation and enhancement of carbon stocks are important factors in climate protection. For example, sustainable forest management promotes leaving high stumps in the logged forest and setting more sustainable and realistic profit targets to let wood grow longer and absorb carbon. Even in under intensive forest management, some forest areas can be left untouched as reserves for biodiversity conservation. This means a longer life cycle, avoiding excessive tillage and leaving forest vegetation after a timber harvest. In addition, reducing peat extraction and the draining of swamps are effective methods to reduce greenhouse gas emissions.

Food production is a basic condition for human life. Agriculture is the cultivation of the soil – the taking care of cultivable land – and therefore crops play an important role in tackling climate change. A significant amount of human generated atmospheric carbon dioxide would be possible to return into the soil by specific agricultural practices. Carbon sequestration rates in fields can be boosted by taking care of the wellbeing of soil microbes and adding organic plant matter (such as roots, crop residues, manure) to the soil.

Many innovations using biological principles can be used to combat climate change. Examples of these are advances in circular economy, bio-economy and biotechnology based on the cycles of ecosystems. The ultimate goal is to shift towards a more sustainable society where products and raw materials circulate as long as possible and maximize resources. In other words, it requires a transition from a linear “from raw material to product and waste” economy to a business model according to the principles of natural ecosystems. Such closed loop models do not produce waste. Instead, they incorporate residues or waste from one stage of a cycle into raw material for another stage within the same cycle, or for use in a completely different cycle. A circular economy promotes low consumption and high utilization of natural resources, energy and material efficiency. It therefore also produces less greenhouse gas emissions.

The definitions of bio-economy can vary depending on the context and actors. According to one of the many definitions, it encompasses all varieties of production based on renewable natural materials, including the further development and use of innovations and technologies related to such materials. It also promotes systemic change from non-renewable resources to renewable resources. As well as agriculture, many other major industries make up the bio-economy including forestry, chemical, agriculture and food industries, and even ecotourism can be considered part of it.

Even if climate change mitigation would be successful and exceed all expectations, we should nevertheless be prepared to face its consequences at least for many decades. The following conservation actions may be useful in adaptation:

• Conserving mangrove forests and other coastal wetlands helps to prevent coastal flooding and erosion.
• Forest conservation and restoration prevents landslides and helps to regulate the low of waters.
• Diverse practices in forestry and agriculture help us to survive in a changing climate and guarantee food production.
• Sustainable management of highland wetlands and floodplains helps to regulate the flow of water and water quality.
• Conserving biodiversity in agricultural production systems, including the establishment of gene banks for animals and crops.

Here are some suggestions on how to practice influencing skills in biology class:

• Find out about the situation of your local protected areas and get involved if necessary.
• Visit environmental authorities and planners in your municipality and find out about their role in conserving biodiversity and tackling climate change.
• Find out about the climate change mitigation projects in your country, municipality and other countries and get involved.
• Learn about national and international environmental organizations contributing to climate change mitigation.
• Learn about businesses and companies contributing to climate change mitigation or biodiversity conservation.
• Ask students to design a project, which aims to help the school become more climate-friendly, and encourage them to make it happen.