Ecological restoration, or ecosystem restoration, is the process of helping ecosystems that have been harmed, damaged, destroyed, or changed return to a healthier state. It is different from conservation because it focuses on fixing ecosystems that are already damaged, rather than preventing damage before it happens. Ecological restoration can help reduce the loss of plant and animal species, fight climate change, support the benefits that ecosystems provide to people, and help local communities. The United Nations has declared 2021–2030 as the Decade on Ecosystem Restoration to highlight the importance of this work.

Habitat restoration is the intentional effort to improve a specific area so that a functional ecosystem can return. This process may not always match the ecosystem’s original state from the past. To restore habitats successfully, it is important to understand how species live, interact, and depend on resources like food, water, nutrients, space, and shelter.

Scientists believe the current rate of species extinction, known as the Holocene extinction, is 1,000 to 10,000 times faster than the natural, background rate of extinction. Loss of habitat is a major cause of species extinction and the decline of ecosystem benefits. Two main methods to slow these problems are protecting healthy habitats and restoring damaged habitats. In recent years, the number and size of ecological restoration projects have grown very quickly, with hundreds of thousands of projects happening worldwide.

Restoration goals depend on political decisions and vary based on location and culture. Globally, the idea of "nature-positive" has been introduced as a goal to fully recover natural ecosystems by 2050, including restoring damaged ecosystems to reduce the loss of biodiversity.

Ecological restoration has become a key strategy worldwide for protecting biodiversity and maintaining the benefits that ecosystems provide. Restoration efforts often aim to return ecosystems to their original conditions or improve their health and ability to function properly.

Definition

The Society for Ecological Restoration says that restoration is "the process of helping an ecosystem recover if it has been harmed, broken, or destroyed." Restoration ecology is the study of how to restore ecosystems, while ecological restoration is the actual work done by people to fix damaged ecosystems. Ecological restoration uses many different methods, such as controlling erosion, planting trees, removing non-native plants and weeds, growing plants in areas that have been disturbed, making streams visible again, bringing back native animals, improving habitats for specific animals, and creating paths for wildlife to move safely. Many experts believe that restoring ecosystems should involve local people and groups, and they call this process "social-ecological restoration."

The goal of restoring an ecosystem depends on the situation in each area. In the past, the main aim was to return ecosystems to a previous condition, called a "historic baseline," because people thought that past conditions were the best or most natural state. However, this idea is now questioned because human activities, like climate change, keep changing ecosystems, leading to a "shifting baseline." Today, it is widely accepted that there may be several possible goals for restoration, depending on factors such as how badly the ecosystem is damaged, how much of its function can be recovered, what local communities think, and how much restoration will cost.

Restoration efforts aim to help ecosystems support themselves and encourage natural interactions between living things in the environment.

Rationale

There are many reasons to restore ecosystems. These include:

• Restoring natural resources such as clean water or wildlife populations
• Fixing damage to the environment
• Helping human communities and ecosystems adapt to climate change (through ecosystem-based adaptation)
• Reducing the effects of climate change (e.g., by storing carbon dioxide)
• Protecting animals that are at risk of disappearing
• Improving the appearance of natural areas
• Moral reasons: Humans have caused harm to many habitats, and there is a responsibility to fix this damage
• Managing the use of natural resources, especially for people who rely on them for survival
• Cultural value to Indigenous peoples
• Improving the health of people living near ecosystems

People disagree about how to set goals for restoration and what success means. As Laura J. Martin writes, "Restoration goals involve moral and political choices, as well as scientific and practical ones." Some experts support active restoration, such as removing invasive animals, while others believe protected areas should have very little human interference, such as allowing animals to return naturally.

Some people are unsure if the benefits of restoration are worth the cost or point to past failures. It can be hard to set goals because, as Anthony Bradshaw writes, "ecosystems are not unchanging, but in a state of balance that constantly shifts." Some scientists say that even if an ecosystem cannot return to its original condition, a "novel ecosystem" can still be useful.

Restoration can help reduce climate change through activities like planting trees. However, planting trees can harm biodiversity, especially in tropical savannas. The effects of tree planting on water supply and quality depend on the region, climate, and age of the project. Using forests to offset carbon emissions is controversial and sometimes criticized as unfair. In the United States, the Clean Water Act often requires restoring water systems that have been damaged by development or other activities.

Theoretical foundations

Ecological restoration uses many different ideas from ecology.

Disturbance is a change in the environment that stops an ecosystem from working properly. Disturbances can happen in different ways and at different times, and they are a natural part of many ecosystems. For example, some forest and grassland restorations use fire as a natural way to change the environment. However, the harm caused by humans has increased over the past few centuries. It is important to tell the difference between human-caused and natural disturbances so we can learn how to restore natural processes and reduce harm to ecosystems.

Ecological succession is the way a group of living things changes over time, especially after a disturbance. In many cases, an ecosystem starts with a simple group of plants and then becomes more complex with many different species that depend on each other. Restoration often helps this process by starting it, helping it, or speeding it up, depending on how bad the disturbance was. After small or medium disturbances, restoration may involve helping nature recover faster through careful planning. However, after very serious disturbances, like in cities, restoration may need a lot of work to recreate conditions that help natural processes happen again.

Habitat fragmentation is when ecosystems are broken into smaller parts because of changes in how land is used, such as farming, or because of natural events. This makes populations smaller and more separated. Smaller and separated populations are more likely to go extinct. Breaking ecosystems into pieces also makes the habitat worse. The edges of these broken areas have different conditions than the inside, so they support different kinds of plants and animals. Restorative projects can help by adding more suitable habitat and connecting broken areas with paths of habitat. Fixing the effects of fragmentation is an important part of restoring ecosystems. The land around a restoration site can also affect how well it works. For example, a site near existing plants is more likely to grow naturally through seed spread than one that is far away.

Ecosystem function includes the most basic and important processes in natural systems, like how nutrients move and how energy flows. Understanding these processes is needed to fix any problems in ecosystems. These functions come from the whole system working together, so watching and managing ecosystems is important for keeping them stable long-term. The goal of restoration is to create an ecosystem that can support itself completely and work well on its own. To reach this goal, we must understand which parts of an ecosystem influence others so we can restore the functions we want.

Community assembly is a way to explain how all ideas in community ecology can be connected into one big idea. This theory tries to explain why similar places can have different groups of plants and animals. It assumes that species have similar needs, so the way a community forms depends on random changes from a shared group of species. If all species are similar in how they live, then differences in how they move, spread, or disappear from a place can explain why similar places have different species.

Genetic diversity is just as important as species diversity for restoring ecosystems. Because of this, ecological restorations are now including genetic factors in their plans. Important genetic processes to think about in restored populations include founder effects, inbreeding depression, outbreeding depression, genetic drift, maladaptation, and gene flow. These processes can help predict whether a species will survive in a restored area.

Applications

Leaf litter accumulation is important during the restoration process. More leaf litter helps keep the area more humid, which is needed for plants to grow. How leaf litter builds up depends on things like wind and the types of trees in the forest. Primary forests have more leaf litter, which is deeper and holds more moisture than in secondary forests. These details are important when planning a restoration project.

The uneven spread of resources can affect how plants grow and what types of plants are found in an area. In a study by Baer et al. (2005), researchers changed how resources were spread in a prairie restoration project. They found that making resources more uneven did not always lead to more plant diversity, especially when one plant type dominated. Their results matched theories about how environmental conditions influence which plants grow together. A plant that is best suited to the environment can strongly influence which plants are present.

Restoration is used to help reduce the spread of invasive plants in several ways. One method focuses on reducing invasive plants first. This approach uses techniques that differ from typical restoration projects. The goal is not always to restore an entire ecosystem but to reduce invasive plants. These projects often use a few types of strong native plants planted densely. They are not always managed after planting. These efforts target areas where invasive plants are very common. The goal is to remove invasive plants and reduce the number of their seeds spreading. An example is using insects that eat invasive plants while planting native plants that use the space left behind. These methods work well to reduce weeds, but they may need more help, like mowing or re-planting, to last long-term.

Restoration projects also help scientists learn what makes an ecosystem less likely to be invaded by non-native plants. Because restoration projects use many different methods, they allow scientists to test ideas about how ecosystems work. Studies show that prairies with more plant types have fewer invasions. Research on plant roles shows that prairies with more varied plant functions have fewer invasions. Studies also show that using native plants similar to invasive plants helps them compete better. Scientists use different restoration methods to find the best ways to control invasions. To make restoration a proper science, researchers need to understand what causes restored ecosystems to develop. Using data from past projects can help connect plant traits to their success in restoration.

Progress toward a desired type of ecosystem can be hard if multiple stable states are possible. A study of wetland restoration over 40 years found that unexpected plant growth might mean the environment is not right for the target plants. Ecosystems can change in unexpected ways, but limiting environmental conditions to a narrow range can help guide the changes toward the desired result.

A study looked at how changing diets in high-income countries and restoring land could help reduce climate change. The study found that eating less meat could cut emissions from food production by 61% and store up to 98.3 GtCO2 equivalent, which is about 14 years of current global agricultural emissions. These results are called a "double climate dividend."

Most restoration projects suggest using plants from local areas to increase success and avoid problems from using plants not adapted to the area. However, what "local" means can vary by plant, habitat, and region. The US Forest Service created seed zones based on winter temperatures, dryness, and ecoregions. Some guidelines suggest using seeds from areas with similar environmental conditions, whether now or under future climate changes. For example, using seeds from farther away that match the environment better helped a restoration project more than using nearby seeds. New methods are studying how genes and environments interact to find the best seed sources for each area.

Challenges

Some people think ecosystem restoration is not practical because projects often fail to meet their goals. Hilderbrand and others note that uncertainty about how ecosystems work, how species interact, and other factors is often not considered. Also, the time needed for full restoration is often set too short, and other important steps are ignored or shortened because of practical challenges. In some cases, an ecosystem may be too damaged, and the best choice might be to let it recover naturally without human help. Local communities sometimes oppose restorations that involve adding large predators or plants that need regular fires, as these can threaten people living nearby. High costs can also make restoration seem like a negative outcome.

Restoration results can vary because of past land use, climate change, and how species interact. Public opinion is important for the success of restoration projects. If people believe the costs are too high compared to the benefits, they may not support the project.

Many past restoration projects failed because goals were not clearly defined or because people did not fully understand how ecosystems work. Peter Alpert said, "People may not always know how to manage natural systems effectively." Many people also assume that a restoration plan that worked in one area will work the same way in another, but this is not always true.

A challenge is the difference between restoration ecology (the science) and actual restoration work. Many people in the field believe that science is not used enough in real projects. A 2009 survey found that the gap between science and practice was the second most common reason for problems in restoration efforts.

Scientists and practitioners have different ideas about why this gap exists. One issue is that research questions studied by scientists are not always helpful for land managers. For example, many studies describe problems in detail but do not offer clear solutions. Also, many studies are done in controlled environments or on small scales, which may not match real-world conditions. These small-scale experiments may not show how things work in actual restorations. One way to address this is the development of International Principles & Standards for Ecological Restoration, but some scientists think these rules are too strict and prefer more flexible guidelines.

Another problem is that scientists who want to collect large-scale data on restoration projects often face challenges. Managers may not collect or keep enough data, and some agencies only keep a few physical copies, making it hard for researchers to access information. Many projects also lack time and money for proper data collection, which limits scientists' ability to study and improve restoration efforts.

Agriculture causes environmental harm, but it is important to balance food needs with restoration efforts. Restoration frameworks help make decisions by reducing conflicts between restoring ecosystems and producing food. For example, agroforestry is becoming a popular method for restoring ecosystems, especially in areas with large farming operations.

Climate benefits from restoring nature are much smaller than the effects of ongoing fossil fuel use. Relying too much on land for climate solutions may delay the need to stop using fossil fuels. Even though restoration is getting more attention, scientists say that restoring land is important for fighting climate change but cannot replace the need to reduce fossil fuel use quickly. This is because restoration efforts may not happen fast enough to significantly lower global temperatures in the coming decades.

Studies show that avoiding deforestation is better than allowing it and then reforesting later. Deforestation causes long-term loss of biodiversity and soil damage. Younger boreal forests are more likely to release stored carbon from the soil. Damage to tropical rainforests may have been underestimated until about 2019. The benefits of reforestation will take many years to appear, while protecting existing forests provides faster carbon storage benefits. Scientists believe that protecting and restoring carbon-rich ecosystems, like natural forests, is the best way to address climate change.

Contrasting restoration ecology and conservation biology

Restoration ecologists and conservation biologists both agree that protecting and restoring habitats is essential for preserving biodiversity. However, conservation biology mainly focuses on population biology, which studies how animal and plant populations grow and change. Because of this, conservation biology often examines specific groups of animals, such as endangered species, at the level of their genetic makeup within populations. Restoration ecology, on the other hand, works at the community level, looking at larger groups of plants and animals within ecosystems.

Conservation biology often focuses on vertebrate animals (like mammals, birds, and fish) and invertebrates (like insects) because these animals are well-known and widely studied. Restoration ecology, however, typically focuses on plants because many restoration projects begin by planting native plant communities. Although restoration ecology emphasizes plants, some ecosystems and projects use "umbrella species" to guide conservation efforts. For example, the Monarch butterfly is an umbrella species for restoring milkweed plant habitats, as Monarch butterflies rely on milkweed plants to lay their eggs and raise their young.

Finally, restoration ecology places a strong emphasis on soil health, the structure of soil, fungi, and microorganisms. This is because healthy soil is the foundation of all functioning land-based ecosystems.

International Principles & Standards for the Practice of Ecological Restoration

The Society for Ecological Restoration (SER) published the second edition of the International Standards for the Practice of Ecological Restoration on September 27, 2019, in Cape Town, South Africa, during SER's 8th World Conference on Ecological Restoration. This publication offers updated and more detailed guidance on how to carry out ecological restoration. It explains the range of ecological restoration and related environmental repair activities. It also includes ideas and input from a group of scientists and professionals from many countries around the world.

The second edition improves on the first edition, which was released on December 12, 2016, at the Convention on Biological Diversity's 13th Conference of the Parties in Cancun, Mexico. The creation of these Standards involved many people. The first edition was shared with many practitioners and experts for their feedback and review. After the first edition was published, SER held workshops and meetings to listen to opinions, asked for input from important international partners and groups, opened a survey for members, affiliates, and supporters, and looked at and answered criticisms that were published.

The International Principles and Standards for the Practice of Ecological Restoration:

• Provide a strong framework to help restoration projects reach their goals.
• Address challenges such as designing and carrying out restoration work, dealing with complex ecosystems (especially in the context of climate change), and balancing different needs related to land use.
• Show how ecological restoration connects social, community, productivity, and sustainability goals.
• Suggest ways for industries, communities, and governments to measure the success of restoration activities.
• Add more methods for planning, carrying out, and monitoring restoration work, including how to assess sites, find examples of healthy ecosystems, use natural regrowth, and participate in global restoration efforts.
• Include more definitions for terms used in ecological restoration.
• Provide a section on how to obtain seeds and other materials needed for restoration projects.

Implementation by country/region

Indigenous peoples, land managers, stewards, and ordinary people have practiced ecological restoration or ecological management for thousands of years. Restoration ecology became a separate field in ecology during the late twentieth century. The term was created by John Aber and William Jordan III while they worked at the University of Wisconsin–Madison.

In 2024, the European Union passed a nature restoration law. This law aims to restore 20% of degraded ecosystems by 2030 and 100% by 2050. The representative of Austria, Leonore Gewessler, voted against the decision made by her government. She may face up to 10 years in prison for this action.

Before ecology became a scientific discipline, large-scale restoration began with efforts to restore big game populations in the early 20th century. The first native plant restoration project in the United States was started in 1907 by Eloise Butler in Minneapolis, Minnesota. This was followed by the Vassar College Ecological Laboratory restoration program, created in 1921 by Professor Edith Roberts. The first tallgrass prairie restoration was the 1936 Curtis Prairie at the University of Wisconsin–Madison Arboretum. Workers from the Civilian Conservation Corps replanted prairie species on a former horse pasture, guided by university faculty including Aldo Leopold, Theodore Sperry, Henry C. Greene, and John T. Curtis. The UW Arboretum became a major center for tallgrass prairie research in the first half of the 20th century and for studying techniques like prescribed burning. This was followed by the 40-hectare Schulenberg Prairie at the Morton Arboretum, started in 1962 by Ray Schulenberg and Robert Betz. Betz later worked with The Nature Conservancy to create the 260-hectare Fermi National Laboratory tallgrass prairie in 1974. Restoration ecology became a distinct sub-discipline of ecology and natural resources management as the number of protected natural areas increased in the 1980s. In 1997, the National Wildlife Federation signed a memorandum of understanding with the Intertribal Bison Cooperative, the first conservation agreement between an environmental organization and an inter-tribal group. This agreement aimed to support the restoration of wild bison to tribal lands. Anishinaabek/Neshnabék communities across the Great Lakes region are leading ecological restoration projects. Kyle Whyte, a representative, explained that these projects "seek to learn from, adapt, and put into practice local human and nonhuman relationships and stories at the convergence of deep Anishinaabe history and the disruptiveness of industrial settler campaigns."

Australia has been the site of historically significant ecological restoration projects, beginning in the 1930s. These projects responded to environmental damage caused by colonizing settlers after the forced removal of First Nations communities. The Traditional Ecological Knowledge of First Nations communities was not used in these early projects.

Many of the first Australian restoration projects were started by volunteers, often through community groups. These volunteers often used scientific resources, such as botanical and ecological knowledge. Local and state government agencies, as well as industry, also participated. Australian scientists became increasingly involved in restoration efforts. One notable scientist was Professor T G Osborn, a botanist and plant ecologist from the University of Adelaide. In the 1920s, he conducted pioneering research on the causes of vegetation degradation in arid zones. From this time, Australian botanists, plant ecologists, and soil erosion researchers focused more on restoring ecological functioning in degraded areas.

The earliest known attempt by Australian settlers to restore a degraded natural ecosystem began in 1896 at Nairm (known to the Kulin nation as Port Phillip Bay, Melbourne). Local government and community groups replanted degraded areas of the foreshore reserves with the indigenous plant species, coastal teatree (Leptospermum laevigatum). These projects aimed to preserve recreation sites and promote tourism. However, some residents, including Donald Macdonald, a journalist and nature writer, were concerned about the loss of biological qualities and campaigned to fully restore the teatree ecosystems and protect their native wildlife.

Degraded arid-zone regions in Australia were the focus of historical ecological restoration projects. Pastoral industries in South Australia and New South Wales caused significant environmental damage by 1900, leading to severe wind erosion. Starting around 1930, Australian pastoralists began revegetation projects to restore indigenous flora in these degraded areas.

At his Koonamore research station in South Australia, established in 1925, Professor T G Osborn studied the loss of indigenous vegetation caused by overstocking and wind erosion. He concluded that restoring indigenous saltbush (Atriplex spp.), bluebush (Maireana spp.), and mulga (Acacia aneura) vegetation was possible if degraded land was protected from livestock and allowed to regenerate naturally. Influenced by Osborn’s research, South Australian pastoralists adopted this technique in the 1930s. For example, at Wirraminna station, fencing excluded livestock, and severe soil drifts were fully revegetated through natural regeneration. Furrowing (ploughing) of eroded areas also helped indigenous vegetation regenerate naturally. These efforts were so successful that the South Australian government adopted them as official soil conservation policies in 1936. Legislation to support these policies was passed in 1939.

In 1936, mining assayer Albert Morris and his restoration colleagues started the Broken Hill regeneration area project. This project focused on the natural regeneration of indigenous flora on a severely wind-eroded site in western New South Wales. Local and state governments, along with the Broken Hill mining industry, supported and funded the project. Because the project was well-suited to arid conditions, the New South Wales government used it as a model for restoring 20 million hectares of severely eroded land in the western part of the state. Legislation to support this effort was passed in 1949.

Another early Australian restoration project occurred on the north coast of New South Wales. Beginning around 1840, settlers occupied coastal areas, displaced First Nations communities, destroyed large areas of biologically diverse rainforest, and converted the land to farms. Only small patches of rainforest remained. In 1935, dairy farmer Ambrose Crawford began restoring a degraded four-acre (1.7-hectare) patch of local rainforest, known as "Big Scrub" (Lowland Tropical Rainforest), at Lumley Park reserve in Alstonville. His methods included removing invasive weeds and planting indigenous rainforest species. Crawford worked with professional government botanists and received support from his local government council. The restored rainforest reserve still exists today.

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Traditional ecological knowledge

Traditional ecological knowledge (TEK) from Indigenous Peoples shows that restoration ecology is a practice that has existed for thousands of years. Indigenous people have learned about the environment through careful observation, experience, and managing natural resources. In the past, they shaped their surroundings to meet their needs, such as food, water, shelter, and medicine, while also improving the health of plants, animals, and the environment. This helped them build a strong connection with nature and pass down important lessons through their culture.

Because of their deep understanding of the land, local Indigenous people have valuable knowledge that can help restore ecosystems. Their way of using natural resources includes respect for cultural, social, and environmental factors, as they have lived closely with plants and animals for many generations. Their livelihoods depend on the environment, so they have developed detailed knowledge about how to care for it.

Restoration ecologists must remember that TEK is specific to certain places because of the close relationship Indigenous Peoples have with the land. When working with Indigenous Peoples to include their knowledge in restoration projects, it is important to avoid taking their knowledge without permission. For successful restoration that includes Indigenous Peoples, Indigenous leaders should guide the process to ensure that non-Indigenous people recognize the unequal power relationships. One way to do this is by using the "walking on two legs" framework, created by Secwépemc elder Chief Dr. Ronald E. Ignice. This idea compares TEK and Western knowledge to two legs that must both be led by Indigenous Peoples.

For example, the California Indians used careful and detailed methods to manage their environment, including controlled burning of forests and specific farming techniques. They had a deep understanding of how to use fire, grow plants, and identify which plants were safe to eat. They also knew how to manage wildlife, such as tracking the number and variety of large animals. Today, while the United States has set aside land to protect habitats from human harm, Indigenous practices can still help restore ecosystems and manage wildlife.

Related journals

• Restoration Ecology, a journal published by the Society for Ecological Restoration (SER)
• Ecological Management & Restoration, a publication of the Ecological Society of Australia (ESA)
• Ecological Restoration, a journal published by the University of Wisconsin Press