Tropical forests cover less than half of the world's forested land, yet between them they hold carbon equivalent to about a third of everything currently in our atmosphere. Old-growth rainforest, forest that has never been cleared, holds the lion's share of it, locked away in trunks, branches and roots that have been growing for centuries.
But not every old-growth forest stores the same amount of carbon, even under similar climates. That's the puzzle a team of researchers, including scientists based at James Cook University in Cairns, just up the road from the Daintree, set out to unravel in a newly published study in Nature's Scientific Reports. Drawing on more than 2,000 old-growth forest plots spanning Central America, South America, Africa, Asia and Oceania, they looked at how climate, soil and slope shape the carbon stored in a forest's living biomass. What they found is more interesting than a simple "warmer means less carbon" story.
Structure, not just climate
Climate does shape a forest's carbon store, the study found, but mostly indirectly, through its effect on forest structure. Things like the density of the wood, the average size of trees and how many trees grow in a given area all respond to climate. The catch is that they often respond in opposite directions to one another, cancelling each other out.
The result: across the tropics, there was no simple, universal relationship between climate and carbon storage. What mattered more was a region's biogeographic history, its own long, unique evolutionary story, shaped over millions of years by continental drift, glaciation and the slow emergence of new species.
Hope's Cycad on Lot 157, a protected property.
It's a finding that resonates with our name. Long before Australia broke away from the ancient supercontinent Gondwana, the ancestors of trees still growing in the Daintree today were already there. That deep history is written into the forest's structure and, this study suggests, into how much carbon it holds.
Why old-growth forest can't be replaced overnight
The researchers also noted something sobering. On average, cleared tropical forest takes around 120 years to rebuild the carbon stores of old-growth forest. A century, at least, to get back what took a single afternoon of clearing to lose.
Clearing on Lot 26, a property we purchased for conservation.
What this means for the Daintree
Much of the Daintree's lowland rainforest is old-growth, still holding the carbon it has built up over thousands of years. It's also freehold land, some of it legally able to be cleared for housing.
Every property Gondwana Rainforest Trust purchases keeps a stand of mature rainforest exactly where it is: carbon intact, structure intact, history intact. It's not a substitute for planting new trees. It's protecting a vault of carbon that no amount of replanting could quickly rebuild.
When you help us purchase and protect a Daintree property, you're keeping one of the world's oldest carbon stores standing, for the climate, and for every species that calls it home.