In a new commentary published on 2 April in Nature, experts urge the restoration community, forestry experts, and policymakers to focus on regenerating natural forests (1). They argue that restoring natural forests on degraded land is the cheapest and easiest way to lock up atmospheric carbon and meet the 1.5 degrees Celcius climate goals. Plantations are less effective at storing carbon.
“To stem global warming, deforestation must stop,” the authors write. The International Panel on Climate Change (IPCC) states that increasing the area covered by forests, woodlands, and woody savannahs could remove around 25 per cent of the total atmospheric carbon required to limit global warming to 1.5 °C above pre-industrial levels. However, this would require adding 240 thousand square kilometres of forest per year until 2030.
There are three main strategies for restoration:
- Allowing abandoned agricultural land revert to natural forests on their own;
- Converting unprofitable agricultural lands into plantations;
- Growing crops and useful trees together, known as agroforestry.
Out of the 43 countries in the Bonn Challenge, a global effort to restore degraded and deforested lands 24 have shared their restoration plans, which include plantations (45 per cent), natural forests (34 per cent) and agroforestry (21 per cent).
However, plantations store carbon much less effectively, the experts from University College London and the University of Edinburg explain. Therefore, the best approach is turning degraded lands into protected natural forests.
Young forest allowed to flourish reach carbon-storing levels of mature forests within 70 years. This can be accelerated by protecting forests from fire and human impacts and planting native tree species. The best places to target are the tropics and subtropics since trees grow quickly close to the equator, and land is cheap and available.
Unfortunately, the authors write, “clashing priorities are sabotaging carbon storage potential.” Despite the known benefits of natural forests, plantations remain popular, owing to the potential for profit. Crops will be grown on two-thirds of lands promised to global reforestation with many countries planning vast monocultures, including Brazil and China.
The authors believe policymakers are misinterpreting the term ‘forest restoration’ and plantations should not be part of reforestation schemes. They recommend excluding monocultures from the definition of ‘forest restoration.’ Plantations store less carbon ― not much more than the land being cleared to plant them on ― and once crops are harvested, the carbon is released back into the atmosphere as waste plant material decays.
Furthermore, massively increasing the number of plantations will cause “a major shift in global land use” and could have serious economic impacts on growers.
To determine the best reforestation strategy, the researchers looked at four different scenarios: extending current commitments until 2100; then until 2050, after which natural forests are converted to plantations for biofuels; converting all areas to natural forests; everything becomes plantations.
On average, they found that natural forests are 6 times better than agroforestry and 40 times better than plantations at storing carbon.
While there are many challenges and uncertainties, natural forests could make a considerable contribution to keeping global warming under 1.5 degrees Celius. The authors suggest four ways of boosting the likelihood of success:
- Increasing the area of land committed to regenerating natural forests;
- Prioritising natural regeneration in the tropics;
- Better planning, for example, targeting treeless regions for new plantations and choosing agroforestry over monocultures;
- Protecting young forests.
(1) Lewis, S. et al. Restoring natural forests is the best way to remove atmospheric carbon. Nature (2019). DOI: 10.1038/d41586-019-01026-8