Ecological restoration, or ecosystem restoration, is the process of helping ecosystems recover when they have been harmed, damaged, destroyed, or changed. It is different from conservation because it focuses on fixing ecosystems that are already damaged, instead of trying to stop damage before it happens. Ecological restoration can help reduce the loss of plant and animal species, fight climate change, support the natural services that ecosystems provide, and help local communities. The United Nations has declared 2021–2030 as the Decade on Ecosystem Restoration to highlight the importance of restoring ecosystems globally.

Habitat restoration is the intentional effort to repair a specific area so that a healthy ecosystem can return. This process may not always match the ecosystem’s original condition from the past. To succeed, it is important to understand how species live, interact, and what they need to survive, such as food, water, nutrients, space, and shelter.

Scientists believe the current rate of species extinction is 1,000 to 10,000 times faster than the normal, natural rate. Loss of habitat is a major reason for species disappearing and the decline of ecosystem services. Two ways to slow this trend are protecting high-quality habitats and restoring habitats that have been damaged. In recent years, the number and size of ecological restoration projects have grown rapidly, with hundreds of thousands of projects taking place worldwide.

Restoration goals depend on political decisions and vary by region and culture. Globally, the idea of "nature-positive" has become a shared goal to fully recover natural systems by 2050. This includes restoring damaged ecosystems to reduce the loss of biodiversity.

Ecological restoration is now a key strategy for protecting biodiversity and keeping ecosystems healthy. Restoration projects often aim to return ecosystems to their original state or improve their ability to function properly.

Definition

The Society for Ecological Restoration describes restoration as "the process of helping an ecosystem recover if it has been harmed, broken, or lost." Restoration ecology is the scientific study of how to restore ecosystems, while ecological restoration is the actual work done by professionals. Ecological restoration uses many different methods, such as controlling erosion, planting trees, removing non-native plants and weeds, planting vegetation in damaged areas, making streams visible again, bringing back native animals, improving habitats for specific species, and creating paths for wildlife to move safely. Many experts believe that successful restoration must involve local people and groups involved in the area, a process called "social-ecological restoration."

The goal of restoring an ecosystem depends on the unique situation of the area. In the past, the aim was often to return ecosystems to a previous condition, called a "historic baseline," because people thought past states were perfect or ideal. However, this idea is now questioned because human actions, such as climate change, keep changing ecosystems over time, leading to a "shifting baseline." Today, it is widely accepted that restoration goals can vary based on many factors, including how much damage the ecosystem has suffered, how much of its function can realistically be restored, the views of local communities, and the cost of restoration work.

Restoration efforts aim to help ecosystems support themselves and maintain healthy interactions among living things within the environment.

Rationale

There are many reasons to restore ecosystems. These include:

• Restoring important resources such as clean drinking water or wildlife populations
• Fixing damage to the environment
• Helping human communities and the ecosystems they rely on adapt to climate change (through ecosystem-based adaptation)
• Reducing the effects of climate change (for example, by storing carbon)
• Protecting species 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 repair this damage
• Managing the use of natural resources, especially for people who depend on them for survival
• Cultural importance to Indigenous peoples
• Improving the health of nearby human populations

People have different ideas 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 practical and scientific ones." Some restoration efforts involve taking direct action, such as removing invasive animals, while others believe that protected areas should have very little human involvement, like allowing natural processes to return.

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

Restoring ecosystems can help reduce climate change by planting trees, such as in afforestation projects. However, planting trees in certain areas, like tropical savannas, can harm biodiversity. The effects of afforestation on water supply and quality depend on the region, climate, and how long the trees have been growing. Using forests to offset carbon emissions is debated and sometimes criticized as unfair treatment of other countries. In the United States, the Clean Water Act often requires restoring damage to water systems caused 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 normally. Disturbances can happen in many different ways and sizes, and they are a natural part of many ecosystems. For example, some forest and grassland restorations use fire as a natural part of the environment. However, human activities have caused more severe and widespread changes to ecosystems in recent centuries. It is important to tell the difference between human-caused and natural disturbances so that we can learn how to restore natural processes and reduce harm to ecosystems.

Ecological succession is the way an ecosystem changes over time, especially after a disturbance. In many cases, an ecosystem starts with a few simple plants and becomes more complex over time with many different species. Restoration often helps this process by starting, supporting, or speeding it up, depending on how serious the disturbance was. After small or medium disturbances, restoration may help natural changes happen faster with careful management. However, after very serious disturbances, like in urban areas, restoration might need major efforts to recreate conditions that allow natural changes to occur.

Habitat fragmentation is when ecosystems are broken into smaller parts because of changes in how land is used (such as farming) or natural events. This makes ecosystems smaller and more separated. Smaller and more isolated groups of animals and plants are more likely to disappear. Breaking up ecosystems also makes the habitat less healthy. The edges of broken areas have different conditions than the inside, so they support different types of plants and animals. Restoration projects can help by adding more suitable habitat and connecting broken areas with paths that allow animals and plants to move between them. Fixing the effects of fragmentation is an important part of restoring ecosystems. The surrounding landscape also affects how well restoration works. For example, a restoration site near existing plants is more likely to grow naturally because seeds can travel there more easily.

Ecosystem function describes the basic and important processes in natural systems, such as how nutrients move and how energy flows. Understanding these processes is important for fixing problems in ecosystems. Ecosystem functions depend on how all parts of the system work together, so monitoring and managing them is important for keeping ecosystems stable long-term. The goal of restoration is to create an ecosystem that can support itself and function completely on its own. To reach this goal, we need to understand which parts of an ecosystem influence others so we can restore the functions we want.

Community assembly is a way to understand how different species form communities in similar environments. This idea suggests that species have similar needs, so the way a community forms depends on random changes in how species move, settle, and disappear. If all species have similar needs, then differences in how many species are present in similar areas are caused by random changes in how they move and settle.

Genetic diversity is as important as having many different species for restoring ecosystems. Because of this, ecological restorations now consider how genes work when planning projects. Important genetic processes to think about in restored areas include founder effects (when a small group starts a new population), inbreeding depression (health problems from close relatives mating), outbreeding depression (problems from mixing unrelated species), genetic drift (random changes in genes), maladaption (when species are not suited to their environment), and gene flow (how genes move between populations). 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 moist, which is necessary 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 thicker and holds more moisture than in secondary forests. These details are important when planning restoration projects.

The uneven spread of resources can affect the types of plants that grow, how many different plants are present, and how the plant community develops over time. 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 was not enough to ensure many different plant species would grow if one species was already strong across all resource levels. Their results supported the idea that certain conditions can influence which plants grow best.

Restoration is used to reduce the spread of invasive plants in several ways. One method focuses mainly on reducing the number of invasive plants and stopping them from spreading further. This approach often uses different restoration techniques than typical projects. The goal here is not always to restore an entire ecosystem. These projects often use a few types of strong native plants planted in large numbers. They may not be managed after planting. These projects usually target areas where invasive plants are very common. The goal is to first remove invasive plants and then reduce the number of invasive seeds spreading to nearby areas. For example, using insects that eat weeds while planting native plants that can use the space and resources left behind. These methods have worked to reduce weeds, but they may not last long without more help, like mowing or replanting.

Restoration projects also help scientists learn what makes an ecological community less likely to be invaded by non-native species. Because restoration projects use many different methods, they can be used to test ideas about how invasions happen. Scientists have studied how the variety of plants used in restoration affects invasion. Generally, prairies with more different plant species have fewer invasions. Research using functional ecology has shown that prairies with more varied plant roles also have fewer invasions. Studies also show that using native plants with similar traits to invasive plants helps them compete better. Scientists have tested different management strategies in various restoration projects to find the best ways to control invasions. To make restoration ecology a complete science and improve its methods, scientists need to find patterns in how restored communities develop. While new experiments can be created, one way forward is to use data from past restoration studies to see how plant traits affect their success.

Progress toward a desired type of plant growth can be hard if multiple stable plant communities exist. A study of wetland restoration over 40 years found that unexpected plant growth patterns may mean the environment is not right for the plants being restored. Plant growth may not follow expected paths, but limiting environmental conditions to a narrow range can help guide growth toward the desired outcome.

A study measured how much climate change could be reduced if high-income countries changed their diets to eat less meat and restored land that was not used for farming. The study found that changing diets could reduce yearly emissions from food production in these countries by 61% and store up to 98.3 (55.6–143.7) GtCO2 equivalent, which is about 14 years of current global agricultural emissions until natural vegetation grows back. These results are called a "double climate dividend."

For most restoration projects, it is usually best to use plants from nearby areas to increase the chance of success and avoid problems caused by plants not being adapted to the environment. However, what "nearby" means can change based on the plant, habitat, and region. The US Forest Service recently created temporary seed zones based on winter temperature, dryness, and large ecological regions. Some guidelines suggest using seeds from areas with similar environmental conditions, whether now or under future climate changes. For example, in a study about a plant called Castilleja levisecta, seeds from farther away that had similar environmental conditions worked better in the restoration than seeds from closer areas. New methods are also being developed to study how genes and the environment interact to find the best seed sources based on how well plants are adapted to their surroundings.

Challenges

Some people think restoring ecosystems is not practical because restorations often do not reach their goals. Hilderbrand et al. note that uncertainty about how ecosystems work and how species interact is often not considered. Also, the time needed for full restoration is sometimes too short, and important steps are skipped because of practical challenges. In some cases, if an ecosystem is very damaged, letting it recover naturally might be the best choice. Local communities sometimes oppose restorations that bring in large animals or plants that need regular fires, as they worry about risks to people nearby. High costs can also make restoration seem unwise.

Restoration results can vary because of past land use, climate change, and how species interact. Public opinion is important for restoration success. 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 unclear or because people did not fully understand the ecosystem. As Peter Alpert says, "people may not [always] know how to manage natural systems effectively." Some people 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 scientists and workers believe science is not used enough in real projects. A 2009 survey found that the "science-practice gap" was the second most common reason for problems in both science and practice.

This gap happens partly because scientists study questions that are not useful for land managers. For example, some research describes problems in detail but does not offer clear solutions. Many studies are done in small, controlled areas, not in real-world conditions. This makes it hard to know if results apply to larger projects. Scientists have created guidelines for restoration, but some argue these rules are too strict and limit flexibility.

Restoration projects often struggle to collect enough data. Managers may not keep detailed records, and some agencies only have a few physical copies of data, making it hard for researchers to access. Time and money limits also make data collection difficult, which stops scientists from using real data to improve restoration efforts.

Agriculture harms the environment, but restoring ecosystems must not conflict with the need to grow food. Restoration plans help balance land use by reducing conflicts between restoring nature and growing food. For example, agroforestry (growing trees and crops together) is being used more in places with large farms.

Restoring nature helps the climate, but this benefit is much smaller than the harm caused by burning fossil fuels. Relying too much on land for climate solutions might slow efforts to stop using fossil fuels. Even though restoring land is important for fighting climate change, it cannot replace the need to reduce fossil fuel use quickly.

Scientists say it is better to stop cutting down forests than to allow them to be cut down and then regrow later. Cutting forests causes lasting harm to biodiversity and soil. Young boreal forests are more likely to release stored carbon from the soil. Damage to tropical rainforests might have caused more greenhouse gas emissions than previously thought. Reforesting or planting new forests will take many years to help reduce global warming, while protecting existing forests gives faster benefits. Scientists believe protecting and restoring forests that store a lot of carbon is the best way to fight climate change.

Contrasting restoration ecology and conservation biology

Restoration ecologists and conservation biologists both believe that protecting and restoring habitats is essential for preserving biodiversity. However, conservation biology is mainly based on population biology. Because of this, it often studies specific species populations, such as endangered species, at the level of population genetics. Restoration ecology, on the other hand, focuses on communities within ecosystems, looking at broader groups of living things.

Conservation biology often studies vertebrate and invertebrate animals because these species are common and well-known. Restoration ecology, however, places more emphasis on plants. This is because restoration projects usually start by creating plant communities. Although restoration ecology focuses on plants, some ecosystems and projects may use "umbrella species" to guide efforts. For example, the Monarch butterfly is an umbrella species for restoring milkweed plant habitats, as Monarch butterflies need milkweed to reproduce.

Restoration ecology also pays more attention to soils, soil structure, fungi, and microorganisms. These elements are important because they form the base of healthy land 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 perform ecological restoration. It explains the wide range of activities involved in ecological restoration and related environmental repair work. It also includes ideas and input from scientists and professionals from many countries around the world.

The second edition improves on the first edition of the Standards, 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. Before the first edition was published, it was shared with many experts and professionals for their feedback. After the first edition was released, SER held workshops and meetings, asked for input from important international groups, opened a survey for members and supporters, and responded to published comments.

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 planning and carrying out projects well, understanding complex ecosystems (especially in the context of climate change), and balancing different land use needs.
• Emphasize how ecological restoration connects social, community, productivity, and sustainability goals.
• Suggest ways to measure the success of restoration activities for industries, communities, and governments.
• Add more details about practices and actions that help professionals plan, carry out, and monitor restoration projects. These include methods for assessing sites, identifying reference ecosystems, using natural regeneration, and participating in global restoration efforts.
• Include a larger list of terms used in ecological restoration.
• Provide a technical section about how to source seeds and other materials needed for restoration.

Implementation by country/region

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

In 2024, the European Union passed a law to restore 20% of damaged ecosystems by 2030 and 100% by 2050. A representative from Austria, Leonore Gewessler, voted against the government’s decision and may face up to 10 years in prison for doing so.

Before ecology became a scientific field, 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, started by Professor Edith Roberts in 1921. The first tallgrass prairie restoration was the 1936 Curtis Prairie at the University of Wisconsin–Madison Arboretum. Workers from the Civilian Conservation Corps planted prairie species on a former horse pasture, guided by university faculty such as Aldo Leopold, Theodore Sperry, Henry C. Greene, and John T. Curtis. The UW Arboretum was a major center for tallgrass prairie research in the first half of the 20th century and studied methods like prescribed burning. It 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 area of study within ecology and natural resources management as the number of protected natural areas increased in the 1980s. In 1997, the National Wildlife Federation signed an agreement with the Intertribal Bison Cooperative, the first conservation partnership between an environmental group and an inter-tribal group, to support the return of wild bison to tribal lands. Anishinaabek/Neshnabék communities in the Great Lakes region lead ecological restoration projects that, as described by Kyle Whyte, "seek to learn from, adapt, and put into practice local human and nonhuman relationships and stories at the intersection of deep Anishinaabe history and the disruption caused by industrial settlers."

Australia has had important ecological restoration projects since the 1930s. These efforts responded to environmental harm caused by settlers who displaced First Nations communities. The knowledge of First Nations people about traditional ecological practices was not used in these early projects.

Many early Australian restoration projects were started by volunteers, often through community groups. These groups used scientific resources, such as botanical and ecological knowledge. Local and state governments, as well as industry, also participated. Australian scientists became more involved in these efforts. A notable scientist who studied the recovery of damaged ecosystems was Professor T G Osborn, a botanist and plant ecologist from the University of Adelaide. In the 1920s, he researched the causes of vegetation loss in arid regions. From this time, Australian scientists focused more on restoring ecological functions in damaged areas.

The earliest known effort by Australian settlers to restore a damaged ecosystem began in 1896 at Nairm (known to the Kulin people as Port Phillip Bay, near Melbourne). Local government and community groups replanted native coastal teatree (Leptospermum laevigatum) in damaged areas of the foreshore reserves. These projects aimed to protect recreation sites and boost tourism. However, some residents, including journalist and naturalist Donald Macdonald, were concerned about the loss of natural qualities and campaigned to fully restore the teatree ecosystems and protect their native wildlife.

Degraded arid regions in Australia were the focus of historical restoration projects. Pastoral industries in South Australia and New South Wales caused severe environmental damage by around 1900, leading to wind erosion. From about 1930, Australian pastoralists started revegetation projects to restore native plants in these damaged areas.

At his Koonamore research station in South Australia, established in 1925, Professor T G Osborn studied how overstocking led to vegetation loss and wind erosion. He concluded that restoring native plants like saltbushes (Atriplex spp.), bluebushes (Maireana spp.), and mulga (Acacia aneura) was possible if stock was excluded from degraded land and natural regeneration was allowed. Influenced by Osborn’s work, South Australian pastoralists adopted this method in the 1930s

Traditional ecological knowledge

Traditional ecological knowledge (TEK) from Indigenous Peoples shows how restoration ecology has been practiced by humans for thousands of years. Indigenous people have learned about the environment through careful observation, experience, and management of 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 ecosystems and increasing plant and animal life. This close relationship with the environment helped them develop knowledge that is still shared in their cultures today.

Because Indigenous Peoples have lived in specific places for generations, they often have deep knowledge about the land, plants, and animals. Their use of natural resources considers cultural, social, and environmental factors, as they have relied on the environment for survival.

When restoration ecologists work with Indigenous Peoples, they must recognize that TEK is connected to specific places and people. To avoid taking knowledge without permission, it is important to involve Indigenous Peoples in leading restoration efforts. This ensures that non-Indigenous people understand the historical power imbalances and respect Indigenous leadership. 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 guided by Indigenous perspectives.

For example, the California Indians used carefully planned and detailed methods to manage the land, such as controlled burning of forests and growing plants. They had deep knowledge of how to identify edible plants, care for crops, and understand wildlife patterns. Their practices helped maintain healthy ecosystems and animal populations. In the United States, efforts to protect ecosystems by setting aside land from human use could benefit from learning about Indigenous methods, which offer valuable lessons for restoring habitats and managing wildlife.

Related journals

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