Species Reintroduction and Rewilding

Returning lost species to a landscape — through reintroduction and translocation — and restoring ecological processes by rebuilding food webs and key animal populations.

Definition

Reintroduction is the release of an organism into part of its indigenous range from which it has disappeared, one of several conservation translocations. Rewilding is a broader restoration approach that seeks to reinstate self-regulating ecological processes — particularly through restoring populations of keystone, large, or trophically important animals — to recover ecosystem function with reduced ongoing intervention.

Scope

This topic covers the deliberate movement and re-establishment of species for conservation and restoration: reintroduction of locally extinct species, reinforcement of existing populations, conservation translocation and assisted colonization, and rewilding approaches that aim to restore ecological processes through keystone and large-bodied animals. It includes the planning, risk assessment, and post-release monitoring that govern these efforts. It excludes the genetic management of source and recipient populations in detail (treated under conservation genetics) and the general methods of habitat restoration (treated under active and passive restoration techniques).

Core questions

• When is reintroducing a species an appropriate conservation tool?
• What determines whether a reintroduction succeeds or fails?
• How does rewilding aim to restore ecological processes rather than fixed species lists?
• What risks and uncertainties accompany translocation and assisted colonization?

Key concepts

• Reintroduction and reinforcement
• Conservation translocation
• Assisted colonization
• Rewilding and trophic rewilding
• Keystone and ecosystem-engineer species
• Defaunation and trophic downgrading

Key theories

Conservation translocation framework

Moving organisms for conservation spans reinforcement, reintroduction within the indigenous range, and assisted colonization beyond it; each carries different benefits and risks and demands structured feasibility and risk assessment before release.

Trophic rewilding

Restoring populations of large herbivores and predators can reinstate top-down and bottom-up processes — grazing, predation, disturbance, and nutrient transport — that structure ecosystems, aiming for self-regulating function rather than recovery of a precise historical species list.

Clinical relevance

Reintroduction is a core recovery tool for species lost from parts of their range, from large carnivores to plants, and structured guidelines exist precisely because poorly planned releases waste resources and can cause harm, including disease transmission and disruption of recipient communities. Rewilding has reframed restoration goals around ecological function, influencing high-profile programmes and debates over restoring large animals to modern landscapes.

History

Reintroduction matured into a discipline from the late twentieth century, formalized by IUCN guidelines first issued in the 1990s and substantially revised in 2013 to cover the full spectrum of conservation translocations including assisted colonization. Rewilding emerged from 1990s ideas on cores, corridors, and carnivores and broadened in the 2000s and 2010s into trophic rewilding, restoring ecological processes through large-animal populations.

Debates

Assisted colonization and rewilding risks

Moving species beyond their historical range to track climate, or restoring large animals to novel settings, may prevent extinctions and recover function, but critics warn of invasion risk, unpredictable interactions, and the difficulty of choosing appropriate baselines.

Key figures

• Philip Seddon
• Jens-Christian Svenning
• Michael Soule

Seminal works

• iucn2013
• seddon2014
• svenning2016

Frequently asked questions

What is the difference between reintroduction and rewilding?

Reintroduction returns a specific species to an area where it has been lost. Rewilding is broader: it aims to restore natural ecological processes — often by bringing back large herbivores or predators — so the ecosystem can regulate itself with less ongoing human management.

Why do reintroductions sometimes fail?

Common reasons include releasing too few individuals, poor genetic or behavioural preparation, unsuitable or still-degraded habitat, persisting threats such as predators or poaching, and disease. IUCN guidelines exist to assess feasibility and risk before release to improve the odds of success.