Forests and climate change

Forests and climate change Up a tree

KYIV AND SÃO PAULO If the world really loves forests, it should put a price on their carbon

The world’s leaders may quail at closing coalfired power plants or raising natories have recognised that indigenous people are best placed to care for forests petrol prices, but they can be relied upon to embrace one ally in the fight against climate change: the tree. For all his claims that climate change was a hoax, even Donald Trump, as president, championed an initiative to plant a trillion trees. Yet there is cause for scepticism about the pact, announced at the Glasgow climate summit this week, to put an end to deforestation before the decade is out.

The world has seen similar unenforceable declarations before. In 2014 governments, companies and ngos promised to halve deforestation by 2020 and end it by 2030. The first target was missed, making the second, to which many of the same countries have now resubscribed, a stretch. And those trillion trees remain an achievement chiefly of alliteration.

Still, this week’s announcement is more credible than previous pledges. This time, Brazil and Indonesia, both deforestation hotspots, have signed up (India has not). Rich countries have promised to stump up cash to protect and restore forests. All sigthey live in. At least as significant is a commitment from the private sector, including financial institutions, to uproot deforestation from their supply chains and investment portfolios. Slashing, burning or thinning trees or otherwise degrading ecosystems accounts for 11% of emissions. Standing forests, by contrast, serve as carbon “sinks”, breathing in a net 7.6bn tonnes of carbon dioxide each year. Programmes to plant and protect forests will be essential to meeting the Paris agreement’s targets of limiting global average temperature rises to “well below 2°C” above preindustrial levels. The Paris agreement calls for the amount of carbon sequestered each year in sinks to equal or exceed humanmade emissions “in the second half of this century”. This has spurred national and corporate strategies to hit netzero emissions through forestry, from restoring carbonrich peatlands to developing agroforestry. China and India have vast treeplanting programmes. Russia, home to 20% of the world’s forests, wants to use them to offset its sizeable greenhousegas emissions. Bhutan, which plausibly claims to have reached netzero, can do so only by taking credit for a heavy dose of forestry. Myanmar is in a similar situation.

The problem is that the world lacks a shared, sensible system for valuing the contribution of trees to sequestering carbon. This is an accounting puzzle of great complexity. Depending on whether and how it is solved, trees could wind up being either part of the solution to global warming or part of the problem.

The accounting standards now in use and new standards for a carbon market in which forestry offsets can be traded are on the agenda in Glasgow. But quantifying the carbon sequestered by any project, ensuring benefits are durable, providing consistent, transparent dataand weeding out bogus schemes all pose thorny problems.

The natural carbon cycle of forests is selfregulating. Trees soak up CO2 from the atmosphere, then return some of it when they decompose or burn in wildfires. Over time, new plants absorb that CO2.

Humans are distorting things in two ways. Deforestation and forest degradation increase emissions by releasing stored carbon. And the 1.11.3°C of global warming that has come with the 2.5trn tonnes of CO2 already added to the atmosphere further increases carbon emissions: more warming means faster decay and more fires.

At the same time, carbon dioxide from fossil fuels gives plants more to work with,

increasing the effectiveness of some sinks. But this is not an unqualified benefit: trees migrating into the Arctic Circle thanks to “carbondioxide fertilisation” are darkening land that had been snowcovered and white. Darker lands absorb more energy from the sun, amplifying the warming of the polar region.

All these ways humans affect forests, and with them the atmosphere, are devilishly complicated to disentangle from one another—and from what would have happened in their absence. Some standards and methods are in place. Independent scientists and the beancounters of the un Framework Convention on Climate Change have devised a shorthand to help countries measure their exhalation and inhalation of carbon.

In annual greenhousegas inventories that countries submit to the un, changes in emissions in land labelled as “managed” are deemed to be anthropogenic. What falls under “managed” varies by country; it can include everything from pastures on deforested land to protected forests that, while not actively managed, firefighters would defend if spark came to flame. The changes in emissions from managed land thus include natural carbon cycling not directly affected by human activity.

In addition to enabling some fuzziness around what counts, thissystem allows countries to offset industrial emissions against existing forests. For example, Myanmar’s latest greenhousegas inventory shows it emits 8m tonnes of greenhouse gases, while its managed forests soak up 96m tonnes. Although the country still burns fossil fuels, it can claim carbon neutrality under the rules. Myanmar’s emissions are a tiny fraction of the global annual total of 52bn tonnes, so any fudgingdoes not matter much.

The same cannot be said of Russia, the world’s fourthlargest emitter. For years Russia has viewed its vast forests as central to its efforts against climate change. Russia’s commitment to the Paris goals is to reduce its emissions by 2030by 70% relative to 1990 levels, “taking into account the maximum possible absorptive capacity of forests and other ecosystems”. In 2019 Russia claimed its forests absorbed the equivalent of 25% of its emissions.

That effect is declining, as ageing trees soak up smaller amounts of CO2. According to Russia’s Ministry of Environment and Natural Resources, the sink will drop to zero—emitting as much carbon as it absorbs—within 40 years. It was a boon, then, when last year Russia’s first inventory of its forests since the mid1990s found that their volumehad increased by 25%. Earlier this year, astudy published in Nature, a scientific journal, calculated that this carbon sink is 47% greater than previously understood. Much of the increase is because of natural growth, as forests reclaim abandoned agricultural land or trees creep north. Such revisions are worth hundreds of millions of tonnes of carbon emissions, and should show up in Russia’s future inventories.

To add to this windfall, Russiarecently announced it would include unmanaged “reserve” forests alongside managed forests in its greenhousegas inventory. That could improve Russia’s annual reports, if not the climate, by helping to add hundreds of millions of tonnes of CO2 to its forest sink.

The numbers racket Shared standards for measuring the contribution of trees to national emissions would make it easier to compare progress, country by country, towards climate goals. But ecologists have warned that a disconnect between national greenhousegas inventories and the estimates by independent scientists currentlymakes this impossible. Because official greenhousegas inventories count emissions from loosely defined “managed” ecosystems as anthropogenic, and global climate models use a more narrow classification, the two systems yield different results.

According to climate models, Earth's land masses emit 5.5bn tonnes more CO2 each year than the inventories account for. Neither count is better, say the researchers, but since the climate models map out paths to a stable climate, and the inventories track progress along those paths, they are comparing apples and oranges.

This relates to the talks in Glasgow, where delegates will be finalising the guidelines for a “global stocktake” that will see parties to the Paris agreement assess their collective progress towards the Paris goals. For the exercise to be meaningful, it must adjust for the disconnect between national inventories and climate models, or risk giving the impression that governments are doing better than they are.

Improved standards would also create a sounder basis for the growing market in carbon offsets, and thus help marshal the private sector against climate change. For example, Brazilian politicianssee global trading in carbon credits, envisioned in article 6 of the Paris agreement, as a silver bullet for reducing deforestation, the cause of roughly half of Brazil’s emissions. Their thinking is that a global carbon market will turn forests into a tradable commodity, making land in the Amazon more valuable with trees than without.

But to help stabilise the climate, projects that receive carbon credits for stopping deforestation, or promoting reforestation, must be able to demonstrate they are decreasing emissions that would otherwise have taken place—in carbon offset jargon, this is known as additionality. It is possible, for instance, to buy carbon offsets for protecting trees in the Amazonian state of Pará. But most land there is already federally protected, and so should not be seen as a basis for carbon credits.

When it comes to forests, the carbonoffset market is also unable now to factor in what is known as permanence. Replacing a diesel bus with an electric one probably removes emissions for ever: with any luck there will be no diesel buses left to buy when the electric one reaches the end of its life. But a patch of forest can be cleared or burnt in a decade, or even next week. How can the market ensure that offsets bought today have enduring effects? And in Brazil and elsewhere, programmes to reforest or plant new forests come with a leakage problem: saving one bit of land may encourage deforestation elsewhere.

All these problems apply to the existing, voluntary carbon markets. An economy ticket on a flight from London to New York generates some 600kg of CO2; offsets for that carbon can be bought for as little as a few dollars through commercial treeplanting schemes. That may ease a traveller’s conscience but does little to protect the climate. Over the coming fortnight, delegates at cop26 will try to reach agreement on guidelines to assure permanence and account for additionality, in hopes of creating a model that can be emulated in the voluntary markets.

That is all to the good. There is indeed no poem lovely as a tree, and carbon offsets, and the forests they may cause to be planted or protected, can help slow climate change. But for that to happen the world’s leaders will need to demand far less popular measures as well, like ending the use of fossil fuels and transforming farming. Climate models show that ecosystem sinks will be most effective at absorbing CO2 if warming remains in the range of the Paris goals. If temperatures soar, as looks likely, carbonrich tropical ecosystems will dry out, burn and become carbon sources rather than sinks. Trees cannot solve the climate crisis. Only people can. n

A mixed picture

Global forest land change, hectares per year, m

10

Expansion

Deforestation 5

0

-5

-10

-15

-20