Nature Climate Change review urges restoration goals set for ecosystems decades ahead

"Even if temperatures were to stabilize in the near future, nature would continue responding to changes that have already occurred for a very long time," said Tina Heger, an expert in ecological theory and invasion biology at TUM ^[4][5]. That lag is the core of the case. A restoration target copied from a site's past describes conditions the site has already left. On Heger's account, it will keep moving away from them after warming stops.

The reef example shows why the target is hard to pin down. Two lists change there at once, the fish and the corals that house them, and the change in corals alters the habitat the fish depend on ^[10]. A manager restoring a reef to a reference year would be trying to match both.

Heger goes further than calling historical targets impractical. Many habitats are changing so much that native species no longer find the conditions they need ^[8], and holding the old state in place can get in the way. "We may actually hinder the development of new, functioning ecosystems," she said ^[9]. Her replacement is a question about the future. "The key question should no longer be how to maintain a particular ecological state, but how to foster conditions that will support a functioning ecosystem 20, 50 or 100 years from now," she said ^[12].

The authors' own wording is measured. They describe ecological novelty, meaning species communities with no historical precedent, as becoming a defining feature of a rapidly changing world ^[2], and Heger's warning about hindering new ecosystems carries a "may" ^[9]. The control for this argument would be restoration projects aimed at historical states, compared with projects aimed at future function on similar sites. The published summary reports neither.

I think the direction holds for a reef where both fish and corals have turned over. The thing this doesn't tell you is where the line falls for an ordinary site: how far conditions must move before a historical target stops being reachable. A past species list can be checked on a site visit. A target of a functioning ecosystem 50 years out needs an agreed definition of function before anyone can say whether a project met it ^[12].

Heger also frames the change as a personal one. "Watching the world change brings uncertainty and, for many people, a sense of loss," she said ^[14]. Her prescription is to plan for that: "These changes will increasingly affect our lives. That is why the social impacts of climate change should be deliberately incorporated into adaptation strategies, so that we can manage this transformation as effectively as possible" ^[15].