How Much Room Will Nature Need?
50x50 may give nature the room it needs to persist and adapt while protecting the natural systems that help regulate our climate.
Last week, in Conservation Beyond 1.5°C, I ended with a question:
How much room will nature need?
This week, migratory birds gave us another reason to take that question seriously.
A new global assessment from BirdLife International reports that 45 percent of the world's migratory bird species are declining, and one in nine is threatened with extinction. Shorebirds and seabirds are among those faring particularly poorly. Climate change is one of several pressures driving those declines.
BirdLife summarized the problem in language almost anyone can understand:
Birds are running out of places to land.
Think about what migration requires.
A migratory bird doesn't need one protected place. It may need breeding habitat in one country, wintering habitat in another, and a chain of functioning stopover sites stretching thousands of miles between them.
Lose enough links in that chain and protecting the endpoints isn't enough.
A flyway is not simply a route on a map. It is a network of places that must remain sufficiently intact and connected for migration to work.
Migratory birds make last week's question tangible.
How Much Is Enough?
Conservation science has wrestled with some version of that question for decades.
There is no single ecological threshold that applies everywhere. Different species, ecosystems, and landscapes require different amounts and configurations of habitat.
But science can give us a range.
The evidence synthesized in Designing Nature's Half places estimates of terrestrial conservation need between roughly 44 percent and more than 60 percent, depending on what is measured and how conservation need is defined. Other research has proposed retaining roughly half of terrestrial vegetation or designed conservation networks encompassing approximately half the terrestrial realm.
That's why Designing Nature's Half uses 50 percent by 2050 (50x50) as a defensible, precautionary benchmark for ecological sufficiency.
Fifty percent is not a magic number.
And acreage alone isn't enough. What we conserve, its ecological condition, and how conserved areas connect across landscapes all matter.
Climate change makes those connections even more important.
Species distributions shift. Refugia become more important. Coastal ecosystems may need room to migrate inland. Places that seem relatively ordinary today may become important under tomorrow's conditions. The IPCC concludes that maintaining biodiversity and ecosystem resilience globally depends on effective and equitable conservation of approximately 30–50 percent of Earth's land, freshwater, and ocean areas.
So 50x50 isn't simply about conserving where biodiversity exists today.
It is about maintaining enough ecological space for nature to persist and adapt as conditions change.
That was the argument I had been thinking about when I ended last week's essay.
But while working through the climate implications of 50x50, something clicked.
I had been looking at only one side of the argument.
Think of 50x50 as a coin.
One side asks what a changing climate means for nature.
The answer we've been exploring is space: enough connected, functioning ecological space for biodiversity to persist and adapt.
The other side reverses the question: What can conserving nature do for the climate?
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The Other Side of 50x50
The same natural systems we need to conserve for biodiversity also play an important role in regulating climate.
The climate value is substantial. Protecting functioning ecosystems keeps existing carbon stores intact and avoids emissions when those systems are destroyed or degraded. Natural and managed ecosystems also continue removing carbon dioxide from the atmosphere.
Restoring forests, wetlands and peatlands, coastal ecosystems, and soils can also contribute to biological carbon removal.
This is not an alternative to reducing fossil-fuel emissions.
We have to do that too.
But addressing climate change while continuing to destroy natural systems already storing and removing carbon makes little sense.
Climate shapes nature. Nature helps shape climate.
On one side of the 50x50 coin, conserving enough connected and functioning nature gives biodiversity room to persist and adapt as the climate changes.
On the other, conserving those same ecosystems protects natural carbon stores and supports continued biological carbon removal.
What Tomorrow May Need
None of this is merely about landscapes decades from now.
BirdLife is warning today that migratory birds are already running out of functioning places across their flyways.
Meanwhile, a federal rule that took effect September 14 rescinded the Endangered Species Act's longstanding regulatory definition of “harm,” which had included significant habitat modification or degradation when it actually killed or injured protected wildlife. Twenty states and Washington, D.C., are challenging that and other recent ESA changes in court.
The courts will decide the legal questions.
But ecology presents another one:
What happens when the habitat a species needs tomorrow is the habitat we allow to disappear today?
Land conversion doesn't only eliminate habitat being used now.
It can eliminate future possibilities.
A migration stopover disappears. A corridor is severed. A wetland loses the space it needs to migrate. A forest that could have provided habitat, stored carbon, or offered climate refugia decades from now disappears before we recognize its future importance.
Some of those losses can be restored.
Others cannot.
That is why 50x50 matters.
The scientific foundation for the 50 percent benchmark comes primarily from biodiversity: conserving roughly half provides a defensible, precautionary benchmark for ecological sufficiency.
Climate change gives us another reason to take that ambition seriously.
The same conservation that gives nature room to persist and adapt also protects functioning ecological systems that help store and remove carbon.
The coin is 50x50.
Conserve enough nature for life to persist.
Conserve enough room for life to adapt.
Conserve the natural systems already helping regulate our climate.
Two sides of the same coin.
50x50.
