How Do Active Restoration and Natural Regeneration Differ?

• Source of degradation
• Sprouts regrowing
• Grown tree

What you will learn

• Tell active restoration from natural regeneration by what people do.
• Name what to check before choosing either approach.
• Read a research result about the two approaches without over-concluding.

Before you start

No prior knowledge is needed. The article treats the source's "passive restoration" as the natural regeneration approach.

What is natural regeneration?

It is the approach of only reducing or eliminating the sources of degradation and allowing recovery time for the ecosystem. The U.S. Environmental Protection Agency (EPA) calls it passive restoration in its principles of wetland restoration.

According to EPA, in some rivers and streams passive restoration can re-establish stable channels and floodplains, regrow riparian vegetation and improve in-stream habitats without a specific restoration project. In wetlands that were drained or had their hydrology altered, restoring the original hydrological regime may be enough to let time reestablish the native plant community.

• Ground
• People's tools
• Placed sprouts

What is active restoration?

It is the approach where people act directly on the site. The EPA text sets it against passive restoration: before actively altering a restoration site, determine whether passive restoration will be enough for the site to regenerate naturally.

For example, EPA discusses restoring natural structure where stream channels, drainage ditches or shorelines have been altered. Restoring physical features can be necessary for water quality and native biota to recover. The same guidance also describes removing non-native species in some projects. These are concrete changes to the site, beyond stopping degradation and monitoring natural recovery.

• Degraded site
• Natural regeneration
• Active restoration
• Trees returning

How do you choose?

Check the site first. EPA advises determining whether passive restoration will be enough before intervening. Even though it relies on natural processes, it is still necessary to analyse the site's recovery needs and decide whether time and natural processes can meet them.

A meta-analysis of 133 studies in tropical forests, summarised by Yale University, found that when abiotic and biotic factors are controlled for, restoration success in biodiversity and vegetation structure is higher at natural regeneration sites than at active restoration sites. Natural regeneration is also significantly less costly.

This result concerns tropical forests and the two measures named. It does not mean natural regeneration is better everywhere.

• Check the site
• Enough to recover on its own
• Intervention needed

Real-world example

Think of a small cut. Sometimes you only need to avoid knocks and let the skin heal. Sometimes it needs a bandage. You look at the wound first and then choose how to help.

This is only a comparison to help you remember. An ecosystem is not a human body.

Common misunderstandings

Natural regeneration does not mean leaving a site alone. EPA says the site's recovery needs must still be analysed.

A result from tropical forests does not apply to every ecosystem.

Active is not automatically better. The summarised study found the opposite under the conditions it names.

Frequently asked questions

What is passive restoration?

Only reducing or eliminating sources of degradation and allowing recovery time.

When should each approach be chosen?

First check whether passive restoration will be enough; only if it is not is active intervention needed.

Which approach costs less?

The tropical forest study summarised by Yale found natural regeneration significantly less costly.

Summary

• Natural regeneration removes or reduces sources of degradation and waits; active restoration intervenes directly.
• Check whether passive restoration is enough before intervening.
• In tropical forests, restoration success was higher with natural regeneration under the controls the study names.