An ecosystem is a geographic area where plants, animals and other organisms, as well as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic (living) factors, as well as abiotic (nonliving) factors. Biotic factors include plants, animals and other organisms. Abiotic factors include rocks, temperature and humidity.

Every part of an ecosystem depends on every other part, directly or indirectly. A change in the temperature of an ecosystem often affects what plants grow there, for instance. Animals that depend on plants for food and shelter have to adapt to the changes, move to another ecosystem or perish.

Ecosystems can be very large or very small. Tide pools, the ponds left by the ocean as the tide goes out, are complete, tiny ecosystems. Tide pools contain seaweed, a kind of algae that uses photosynthesis to create food. Herbivores, such as abalone (Haliotis), eat the seaweed. Carnivores, such as sea stars, eat other animals in the tide pool, such as clams or mussels. Tide pools depend on the changing level of ocean water. Organisms in the tide pool must be able to survive submersion in seawater and potentially crushing ocean currents when the tide comes in. When the tide goes back out, the organisms must survive sun exposure and hotter temperatures. Plants and animals in the tidepool have adaptations that help them survive. For example, seaweed has a protective coating to keep it from drying out in the sun. In this way, the biotic parts of the ecosystem depend on abiotic factors.

The whole surface of Earth is a series of connected ecosystems. Ecosystems are often connected in a larger biome. Biomes are large sections of land, sea or atmosphere. They are defined by climate, geography and the plants and animals that live there. The five main types of biomes are desert, aquatic, tundra, grassland and forest.

Within each biome, there are many different ecosystems. The desert biomes of the world, for instance, include a wide variety of ecosystems. The Sahara has a hot, arid climate and includes oasis ecosystems that have date palm trees (Phoenix dactylifera), fresh water and animals, such as crocodiles. The Sahara also has dune ecosystems, with winds constantly shifting the landscape. Organisms in these ecosystems, such as monitor lizards (Varanus) and fennec foxes (Vulpes zerda), must be able to survive on in sand dunes for long periods of time. The Sahara even includes abiotic factors carried by wind and fog from a marine environment. The Atlantic Ocean creates cool fogs on the Northwest African coast that make their way over the desert.

In contrast, the Gobi Desert, which stretches across Mongolia and China, is a cold desert with freezing temperatures. Unlike the Sahara, the Gobi has ecosystems based not in sand, but in bare rock. Some grasses are able to grow in the cold, dry climate. As a result, these Gobi ecosystems have grazing animals, such as the goitered gazelle (Gazella subgutturosa) and even takhi (Equus ferus przewalskii), an endangered species of wild horse that had gone extinct in the wild before being reintroduced in the 20th century. Antarctica is also a cold desert biome. Its thick ice sheet allows only a few mosses – which are nutrient poor – to grow, so animal life, like penguin, whale and seal species, must rely on the ocean for food instead of the land.

Threatened Ecosystems

Humans are a part of ecosystems too. Generally, Indigenous people have lived as part of their local ecosystems for generations without overusing their resources. For example, the Indigenous communities of North America’s Great Plains developed a complex lifestyle centered on the bison (Bison bison), a large grazing animal native to the ecosystem of the Great Plains. The cultural centering of these animals largely occurred after the introduction of horses and firearms by European colonizers. Bison were referred to as “buffalo” by both Indigenous and non-Indigenous people for many years, though their scientific name is bison. Many indigenous people of the Great Plains use the word “buffalo” for the animals in cultural contexts. These tribes used bison hides for their homes and clothing, bison meat for food and bison horn for tools. Bison were also a major part of the Indigenous peoples’ spiritual lives, where people honored the animal with ceremonies and prayers. The ecosystem supported tens of millions of bison in the early 1800s as well as tribes, including the Lakota, Blackfeet, Cheyenne and others who depended on the animal for survival.

However, in the mid-to-late 1800s, the U.S. government, knowing how central bison were to Indigenous life, implemented “scorched earth” policies that encouraged the military to kill as many bison as possible. This was genocide, an effort to destroy Indigenous culture and take over tribal land in the central and western parts of the present-day United States. By 1900, there were fewer than 1,000 wild bison. This not only harmed Indigenous livelihoods, but it also harmed the ecosystem. As a result of non-Indigenous people settling on the land, much of the Great Plains is now largely farmland and used for cattle. Iit is one of the most threatened ecosystems in the world. Today, Indigenous people are working to conserve the Northern Great Plains ecosystem, as they did in the past. For example, the Eastern Shoshone Tribe has introduced bison back to the ecosystem and are monitoring and caring for the growing herd, among other conservation efforts.

Tropical rainforest ecosystems surrounding the Amazon River in South America are also under threat. Tropical rainforests have distinct layers that are defined by the different levels of sunlight they receive, and each of these layers has unique plants and animals. Because of this, each layer of the rainforest can be considered its own smaller ecosystem within the larger rainforest ecosystem.

The top layer of the rainforest is called the emergent layer. This is where the tallest trees grow. This layer is exposed to high winds and harsh sun, but still supports animals like birds of prey, monkeys and insects.

The canopy is the next layer. This layer also has tall trees, but they are more densely packed together than in the emergent layer. Forest canopies also include other plants, called epiphytes, which grow directly on branches. Examples of epiphytes are mosses, ferns and orchids. Canopies are also home to the majority of rainforest animals, including keel-billed toucans (Ramphastos sulfuratus) and howler monkeys (Alouatta). Below the canopy is the next layer, the understory. The understory is darker, so it supports plants that thrive in the shade. It also supports many insects and some larger animals like snakes. The forest floor layer is even darker. It is filled with decomposing matter like leaves and branches from higher layers, making it easy for animals who do not climb trees to find food. Giant anteaters (Myrmecophaga tridactyla) and other creatures that help break down matter and aerate the soil make their homes there.

Indigenous people of the Amazon rainforest live off the land in ways that allow the ecosystem thrive. For example, the Yanomami people that live in the rainforests of Venezuela and Brazil do not live in permanent settlements that might degrade the land. Instead, they farm and hunt in an area until the resources are depleted but not completely used up. They then migrate to another area. This allows the rainforest to replenish itself.

However, the rainforest is being destroyed and degraded by people not indigenous to the forest for purposes like farming and mining. International demand—from countries like China and the United State—for beef, rainforest wood and other products has incentivized local farmers and sometimes even South American governments to continue or ignore deforestation. The opportunity to escape poverty incentivizes local people to mine or farm. This is because many countries with rainforests were formerly colonized by Europeans who built economies based on resource extraction. This often left locals impoverished, because colonizing nations depleted the land, did not share extracted resources and did not develop other industries in the colonies. Now, for citizens of formerly colonized nations, it is a challenge to balance the needs of protecting the ecosystem with economic needs and survival.

Still, the destruction of the rainforest comes at a very high cost for the ecosystem. Deforestation degrades the soil and creates and spreads deserts. By cutting down trees, deforestation also contributes to greater greenhouse gasses in the air, which warm the atmosphere and contribute to climate change. Animal populations have shrunk, and some species have disappeared altogether. This disrupts the cycle of life in the smaller ecosystems within the rainforest, which can then affect ecosystems in other parts of the rainforest.

Deforestation comes at a cost for Indigenous communities too. Indigenous people not only lose their land, they may also lose parts of their culture and knowledge. For example, the Yanomami of the Amazon have a strong history and culture of traditional medicine. Many modern medicines have been developed from rainforest plants, so the Yanomami’s knowledge and stewardship of the forest help their people and may allow for new innovation. They live communally and share goods that they produce themselves—all traditions that would be lost without the rainforest ecosystem. Importantly, the rainforest is also culturally significant to the Yanomami. But rainforest loss goes beyond threatening culture for the Yanomami. They are also at risk of dying out completely. The Yanomami have had little contact with other humans, making them more susceptible to disease. Increased contact with miners from outside of their community has resulted in an increased mortality rate among the Yanomami population.

Restoring Ecosystems

Some ecosystems can be restored after damage or destruction, but it may take considerable effort and many years for an ecosystem to fully recover. In 2022, the United Nations (UN) declared a Decade on Ecosystem Restoration to push national, regional, and local governments and groups to work to restore their local ecosystems.

One way to restore ecosystems is to remove the causes of destruction and allow the ecosystem to recover on its own. This typically means cutting down on human involvement and action in the ecosystem. One example of a conservation program that works this way is the Cocos Island National Park, a World Heritage site in Costa Rica. This park is an island that preserves the unique ecosystem of plant and animal life by not allowing human habitation. Because modern fishing boats were depleting marine life in the surrounding waters, the protection of the island was extended to include areas of the ocean as well.

Another way to restore ecosystems is for humans to take more action by purposely changing the ecosystem in a way that would restore it. For example, in the early 1900s, U.S. government programs exterminated wolves (Canis lupus) from Yellowstone National Park, because they were seen as a threat to livestock and big game. However, scientists noticed that removing the wolves threw off the food web in the ecosystem. The elk population ballooned and elk overgrazed. This degraded the vegetation and land. To correct this, a government program reintroduced wolves back into Yellowstone National Park in 1995. Decades later, researchers have noticed positive changes to the ecosystem, such as a growing beaver population. Beavers were able to rebound as the wolf pack grew, because beavers and elk eat the same plants, and the wolves hunted the elk in the park.

People are also attempting to restore coral reefs that have died as a result of rising sea temperatures caused by climate change. Scientists are trying to grow corals that are more temperature resistant to restore some of the damaged reefs. However, without larger efforts to stop climate change, it is unclear how effective these measures will be.

Individual people, cultures and governments are working to preserve ecosystems that are important to them. The government of Ecuador, for instance, recognizes ecosystem rights in the country’s constitution. The so-called Rights of Nature says that nature or Pachamama (Earth), where life is reproduced and exists, has the right to exist, persist, maintain and regenerate its vital cycles, structure, functions and its processes in evolution. Ecuador is home not only to rainforest ecosystems but also mountain ecosystems and the unique ecosystems on the Galapagos Islands.

There are many ways global citizens can help ecosystems thrive. The first step is to learn about different ecosystems, both locally and internationally, to determine the best way to help threatened ecosystems. People can support local conservation groups and follow recommendations about how to interact with local wildlife. On a global level, people can be mindful about the source of products they buy and choose to buy more sustainably and support international organizations that protect ecosystems. Additionally, people can consider political action on a local, regional or international level and pressure government officials to improve and preserve the environment.