We often hear the claim that "forests would grow more and absorb more carbon if humans just left them alone".
Whilst it's true that certain sensitive ecosystems should be protected from economic activity, very often it's active markets that help us to protect forests and even boost them.
In reality, forests can benefit from active markets for products such as sawlogs for construction, smaller wood for furniture and low-grade wood for paper and bioenergy.
This happens because those markets create revenues for landowners, as well as regulations and certifications that ensure a high standard of stewardship.
The result is manifold:
First and foremost, markets make the forest land profitable for its owners, so they ensure it stays as forest rather than allow it to be developed for agriculture or urban uses. This also drives replanting rates, as faster regrowth is important for future revenues.
Secondly, they manage it actively to remove dead, diseased or infested trees. Just as in human populations, diseased or infested trees pose a risk to healthy trees and can reduce the ability of large swathes of forest to absorb carbon. Removing them boosts the forest's health. Dead wood left in the forest also poses a risk as it can be the fuel that allows wildfires and can hamper new growth by reducing light levels on the forest floor. Some decaying material is good for the forest's long-term health, because it replenishes nutrients in the soil, but these levels need to be well managed to ensure the right balance.
Thirdly, markets work to ensure the most appropriate uses for different types of wood. The carbon absorbed by trees gets locked away in the form of wood. This wood is then used primarily for constructing buildings and making furniture, which means the carbon stays locked away in the wood for the lifetime of those buildings and furniture - possibly decades or centuries. Long, straight logs are needed by the construction industry to build buildings and they fetch the highest prices, so that's what drives forestry priorities. The low-grade wood left over (off-cuts, smaller thinnings and misshapen or diseased trees) can be used for pulp, paper and bioenergy pellet markets at the lowest prices. This process divides up the wood and supports a 'best use' approach.
Finally, markets often come with regulations and certifications that stretch all the way up the supply chain to ensure sustainable sourcing. Whilst the bioenergy industry is a very small player in most forest regions, the Sustainable Biomass Program (SBP) works to ensure biomass generators are not causing or contributing to deforestation, among several other measures. The UK's Biomass Sustainability Criteria also ensure UK-based generators do not contribute to land use change, no matter where in the world they source their pellets.
To see this in action, we can look at productivity in forests where markets are active. These graphs, from a study into the effect of demand for wood products on US forests, show that as harvesting activity increases, so does the amount of stock growing in the forest. The graphs measure the amount of forest land in acres (top row), the inventory or amount of wood growing within that acreage (middle row) and growth rates (bottom row). They all map these measures against the amount of wood being harvested in a year. As you can see, there's a clear positive correlation between increased removals and the growth of forests:
But of course the proof of the pudding is in the eating. Have working forests actually increased over time? Still looking at the Southern USA, which is the biggest single supplier region for UK biomass, we can see that Southern US working forests have more than doubled their inventories - the amount of wood growing in the forest - since records began in 1953:
Importantly, this isn't the result of increasing the amount of forest land, which only grew by a few percent in the same period. It shows that these forests effectively became more dense, making more efficient use of the land and increasing the carbon it absorbs - a result mostly caused by active stewardship by humans.
So, the next time someone claims we should just leave all the forests alone, you'll know what to say.