Restore natural forests to sequester carbon: monocrop plantations are no answer
"The regular harvesting and clearing of plantations releases stored CO2 back into the atmosphere every 10–20 years. By contrast, natural forests continue to sequester carbon for many decades[4]."
"To combat climate change, the most effective place to plant trees is in the tropics and subtropics"
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Two workers handle tree saplings being grown to reforest burned areas of Indonesia
Reforesting of burnt areas in Kalimantan province, Indonesia.Credit: Kadir van Lohuizen/NOOR/eyevine
Keeping global warming below 1.5 °C to avoid dangerous climate change1 requires the removal of vast amounts of carbon dioxide from the atmosphere, as well as drastic cuts in emissions. The Intergovernmental Panel on Climate Change (IPCC) suggests that around 730 billion tonnes of CO2 (730 petagrams of CO2, or 199 petagrams of carbon, Pg C) must be taken out of the atmosphere by the end of this century2. That is equivalent to all the CO2 emitted by the United States, the United Kingdom, Germany and China since the Industrial Revolution. No one knows how to capture so much CO2.
Forests must play a part. Locking up carbon in ecosystems is proven, safe and often affordable3. Increasing tree cover has other benefits, from protecting biodiversity to managing water and creating jobs.
The IPCC suggests that boosting the total area of the world’s forests, woodlands and woody savannahs could store around one-quarter of the atmospheric carbon necessary to limit global warming to 1.5 °C above pre-industrial levels2. In the near term, this means adding up to 24 million hectares (Mha) of forest every year from now until 2030.
Policymakers are sowing the seeds. For example, in 2011, the German government and the International Union for Conservation of Nature launched the Bonn Challenge, which aims to restore 350 Mha of forest by 2030. Under this initiative and others, 43 countries across the tropics and subtropics where trees grow quickly, including Brazil, India and China, have committed nearly 300 Mha of degraded land (see Supplementary Information, Table S1). That’s encouraging.
But will this policy work? Here we show that, under current plans, it will not. A closer look at countries’ reports reveals that almost half of the pledged area is set to become plantations of commercial trees (see Table S1). Although these can support local economies, plantations are much poorer at storing carbon than are natural forests, which develop with little or no disturbance from humans. The regular harvesting and clearing of plantations releases stored CO2 back into the atmosphere every 10–20 years. By contrast, natural forests continue to sequester carbon for many decades4.
To stem global warming, deforestation must stop. And restoration programmes worldwide should return all degraded lands to natural forests — and protect them. More carbon must be stored on land, while recognizing competing pressures to deliver food, fuel, fodder and fibre.
We call on the restoration community, forestry experts and policymakers to prioritize the regeneration of natural forests over other types of tree planting — by allowing disturbed lands to recover to their previous high-carbon state. This will entail tightening definitions, transparently reporting plans and outcomes and clearly stating the trade-offs between different uses of land.
Misdirected efforts
To combat climate change, the most effective place to plant trees is in the tropics and subtropics — this is where most forest-restoration commitments are found. Trees grow and take up carbon quickly near the Equator, and land is relatively cheap and available (see go.nature.com/2ogmbmz and ‘Restoration potential’). Establishing forests has little effect on the albedo (reflectivity) of the land surface, unlike at high latitudes, where trees obscure snow that would otherwise reflect solar energy and help to cool the planet. Well-managed forests can also help to alleviate poverty in low-income regions, as well as conserve biodiversity and support the United Nations Sustainable Development Goals — notably, goals 1 (no poverty), 6 (clean water), 11 (sustainable communities), 13 (climate action) and 15 (life on land).
Source:
https://go.nature.com/2ogmbmz"So far, just over half (24) of the countries in the Bonn Challenge and other schemes have published detailed restoration plans, covering two-thirds of the total pledged area (Table S1). Nations are following three main approaches. First, degraded and abandoned agricultural land will be left to return to natural forest on its own. Second, marginal agricultural lands are to be converted into plantations of valuable trees, such as Eucalyptus for paper or Hevea braziliensis for rubber. Third is agroforestry, which involves growing crops and useful trees together."
"Natural regeneration is the cheapest and technically easiest option. Just over one-third (34%) of the total area allocated is to be managed in this way. Protecting land from fire and other human disturbances allows trees to return and forests to flourish, building carbon stocks rapidly to reach the level of a mature forest in roughly 70 years [4]"
"plantations are the most popular restoration plan: 45% of all commitments involve planting vast monocultures of trees as profitable enterprises. "
"plantations hold little more carbon, on average, than the land cleared to plant them. Clearance releases carbon, followed by rapid uptake by fast-growing trees ... But after such trees are harvested and the land is cleared for replanting — typically once a decade — the carbon is released again by the decomposition of plantation waste and products "
"if the entire 350 Mha is given over to natural forests, they would store an additional 42 Pg C by 2100 (see ‘Which strategy?’). Giving the same area exclusively to plantations would sequester just 1 Pg C or, if used only for agroforestry, 7 Pg C. Furthermore, we find, on average, that natural forests are 6 times better than agroforestry and 40 times better than plantations at storing carbon (sequestering 12, 1.9 and 0.3 Pg C per 100 Mha by 2100, respectively"
https://www.nature.com/articles/d41586-019-01026-8sidd
