What is being overlooked in current international climate policy under the Paris Agreement is the crucial role of biodiversity in maintaining healthy ecosystems and their integrity, which keeps carbon stored in forests, not the atmosphere. Healthy ecosystems are more stable and resilient, with a lower risk of trees dying and lower rates of carbon emissions.

The way we currently count carbon stores risk creating incentives to plant new trees rather than protect existing forests. Yet old-growth forests store vastly more carbon than young saplings, which will take decades or even centuries to reach the same size.

Can ending native forest logging help the climate?

We’ll need to go further and ban logging in all native forests in Australia to help meet our net-zero emissions target, while meeting timber demand from better-managed and increased plantations.

Stopping native forest logging avoids the emissions released when forests are cut and burned. It would also allow continued forest growth and regrowth of previously logged areas, which draws down carbon from the atmosphere and increases the amount held in the forest ecosystem.

The natural biodiversity of our native forests makes them more resilient to external disturbances such as climate change. These forests have larger and more stable carbon stocks than logged areas, newly planted forests and plantations.

If we compare forests protected for conservation with those harvested for commodity production in the Victorian Central Highlands, research shows conservation delivers the greatest climate benefits through continued forest growth and accumulating carbon stocks.

There are growing calls to create the Great Forests National Park to the north and east of Melbourne, which would protect a further 355,000 hectares and more than double protected forests in the Central Highlands.

Net zero: deep, rapid, sustained cuts needed

The world’s nations are aiming to reach net zero by mid-century. Meeting this target will require deep and rapid cuts in carbon dioxide emissions as well as pulling carbon out of the atmosphere into land sinks, especially forests.

The land sector is unique in that it can be both a source (logging, agriculture) and a sink (forest regrowth, for instance) for carbon. The natural way forests take up carbon can be increased through natural regrowth or plantations.

Unfortunately, the current approach, based on IPCC guidelines, to counting this type of natural carbon storage can lead to perverse outcomes.

The carbon sink from forest regrowth only counts towards the “removals” part of net zero when it results from changes we make, such as ending native forest logging. It doesn’t count if it’s regrowth after a natural event such as a bushfire. It’s important to count only human-induced changes in our climate targets.

Tree planting, on the other hand, can be counted towards net-zero targets, despite the fact that newly planted trees will take centuries to sequester as much carbon as found in an old-growth forest.

This type of accounting – known as flow-based accounting – can mean a premium is placed on planting and maintaining young forests with high carbon uptake rates, overlooking the substantial benefits of protecting larger trees in native forests.

That is, this approach favours carbon sequestration (the process of taking carbon out of the atmosphere and storing it in wood) over carbon storage (the total carbon stocks already contained in a forest).

A comprehensive approach to forest carbon accounting would recognise both flows of carbon (as sequestration) and carbon stocks (as storage) contribute to the benefits that native forests offer for reducing emissions.

Carbon accounting needs more clarity

This becomes a problem when forests and fossil fuels are included in a net accounting framework, such as the one used in Australia’s national greenhouse gas inventory.

In net accounts, emissions (from fossil fuel and land sectors) within a year are added to removals, which includes the sequestration of carbon into forests and other ecosystems.

Because this type of accounting only counts the flows of carbon – not existing stocks – it omits the climate benefits of protecting existing forests, whose stored carbon dwarfs the amount Australia emits from fossil fuels each year.

But if we separated out targets for the fossil fuel and land sectors, we could properly treat forest carbon stocks as an asset, giving us incentives to protect them.

Another problem with net accounting is it treats all carbon as equivalent, meaning a tonne of carbon sequestered in trees compensates for a tonne of carbon from burned fossil fuels. This has no scientific basis. Carbon dioxide emissions are effectively permanent, as the buried carbon we dig up and burn stays in the atmosphere for millennia, while carbon in trees is temporary in comparison.

As trees grow, their carbon storage compensates for earlier logging and clearing emissions, which is an important climate benefit. But we’re not comparing apples and apples – forest carbon doesn’t compensate for fossil fuel emissions.

Logging bans are important – but no substitute for ending oil and gas

While ending the clearing and logging of native vegetation is vital for both climate and biodiversity, it’s no substitute for preventing emissions from fossil fuels.

To make this clearer, we must urgently set separate targets for emissions cuts for fossil fuels and increased carbon removal in the land sector. This will ensure phasing out fossil fuel use is not delayed by planting trees, and that the carbon stocks of biodiverse and carbon-dense native forests are protected.

Kate Dooley, Research Fellow, School of Geography, Earth and Atmospheric Sciences, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.