Part 1 – Afforestation vs. Reforestation
A key finding of the Intergovernmental Panel on Climate Change’s (IPCC) new special report is that it is likely that some degree of “afforestation” will be needed to limit global warming to 1.5C above pre-industrial levels.
Afforestation involves planting trees in areas that haven’t recently had any tree cover, in order to create a forest. The type of land planted could include areas that have turned into desert (through desertification), places that have long been used for grazing, disused agricultural fields, or industrial areas.
The main goals of afforestation are to serve as a method to reduce atmospheric CO2, to increase soil quality, and to either avoid or reverse desertification. The forests created through afforestation also provide a habitat to local wildlife, create wind breaks, support soil health, and may also help improve water quality.
Afforestation and reforestation have plenty in common — both have the aim of increasing the number of trees —, but there are a few key differences:
- Afforestation is planting trees where none have stood in recent time.
- Reforestation is planting trees in areas that are currently forested, but have lost trees due to fire, disease, or clear-cutting for logging operations
- Both reforestation and afforestation may be done when an area has been deforested. Deforestation occurs due to short-term reasons like logging or fire, or long-term reasons like forests long ago removed in order to graze cattle or grow crops for agriculture.
Afforestation usually involves tree planting in agricultural or other lands that have been abandoned due to poor soil quality or overgrazing. Over time, the soil was depleted, so now not much will grow there. Abandoned urban areas, such as land formerly cleared for buildings that no longer stand, can also be good candidates for smaller afforestation projects.
Afforestation can occur on land where there may or may not have been forests at one point in history. Deforestation may have occurred on lands hundreds of years ago, or there may not be a record of a forest existing in the place targeted for afforestation.
During the last 50 years, afforestation of abandoned lands, usually completely empty, has become more common — especially in the United States and the United Kingdom. Currently, grasslands and pastures throughout Europe are being turned back into forests. China, India, and countries in North and Central Africa, the Middle East, and Australia are all working on afforestation projects.
Carbon capture is usually cited as the primary reason to spend the time and money to commit to afforestation. As a tree grows, it naturally sequesters CO2 into itself and the soil it grows in.
The ultimate goal of drawing down CO2 from the atmosphere is, of course, to help mitigate climate change. Estimates of the amount of CO2 removed from the atmosphere for various afforestation projects vary, but a study that looked at large-scale afforestation potential found that it could remove more than 189 gigatons of carbon by 2095 (current annual emissions of carbon are about 36 gigatons per year).1
But afforestation has many other benefits, which is why communities and governments choose to invest in it. Soils are a key component for two reasons. The first is that soils are able to hold about three times as much carbon as the atmosphere, so they are a critical part of the climate change mitigation puzzle.2 Healthy soils are also important as a natural water filtration system and as a source of nutrition for plants, the animals that eat them, and insects.
Forests can, over time, improve topsoil. Nitrogen is fixed at higher rates in afforested areas, which have also been shown to neutralize soil pH (reducing acidity in acid soils and alkalinity in alkaline soils).3 According to a study published in the journal Nature Communications, more neutral soil may “improve soil fertility and promote ecosystem productivity.”4
A shelterbelt is the name for an afforestation project in an arid or semiarid environment that aims to shelter farmland or crops from wind, which can also reduce soil erosion. In China, for example, an afforestation project was specifically planted to reduce dust storms.5
Part of a shelterbelt also might be used as a source of wood for fuel or income for the local community. In Kyrgyzstan, walnut and fruit trees were planted as part of an afforestation project with the goal of providing both food and income to the local population.6
In addition, research has shown that forests can improve water quality (primarily through reducing runoff into streams), so cleaner water may be a strong motivation for afforestation in some areas.7 However, other studies have revealed that afforestation can disturb the local water circulation systems, at least in the short term, highlighting the importance of analyzing local hydrologic cycles to determine if a new forest will use too much water.8
Trees can also have social benefits, like providing shade areas for people or livestock. And of course, forests can provide habitat for wildlife, especially birds and insects, some of which may be a food source for human beings or contribute to the biodiversity of a place.9
The Process of Creating a Forest
Afforestation isn’t as simple as just planting trees. Depending on the quality of the soil and especially the topsoil, some site preparation is usually necessary. If a duripan (a hard near-impenetrable surface to the soil) has formed, that needs to be broken up and the soil aerated. In other places, weed control might be important before planting. Invasive plants should be removed.
The trees planted need to be carefully chosen to suit the local environment. For example, in arid and semi-arid regions, where afforestation might be needed in areas of desertification, drought-resistant trees are important. In more tropical regions, those trees that will grow best in hot and humid conditions are planted.
Spacing of the trees depends on the ultimate goal of the afforestation project. If it’s a shelterbelt, trees may be planted more closely together. The number of trees also depends on the goals of the project.
Other considerations include prevailing winds (if looking to create a wind block) and the direction of sunlight in different seasons. For example, if an afforestation project is planted near active agricultural fields, it’s important to plan so that sunlight will be able to reach the crops when the trees are grown.
Over time, an afforestation project may need to be maintained depending on its use and aims.
In urban areas, small afforestation projects (such as a vacant lot on the edge of town) can be created following similar steps, but on a different scale. There are even specific plans and organizations that enable fast-growing forests in unused spaces in cities.
Part 1 – Source: Treehugger, June 12, 2021
Part 2 – Afforestation in China
World’s top tree planters
The chart below shows the countries that had the largest amount of planted forest area to 2015. Note, this represents forest areas planted, not total tree cover.
Afforestation projects are happening all over the planet. Here we focus on China.
The chart shows how, from 1990-2015, China planted the largest amount of new forest out of any country in the world, and that by 2015 the amount of planted forest in China covered 79 million hectares – an area more than three times the size of the UK. By 2020 planted forest land area had increased to more than 13.25 million hectares.
Much of this planting was facilitated by the country’s “Grain for Green” programme – which pays farmers to transform their cropland into forest.
Many of these new forests are in a part of China called the Loess plateau, an area the size of France. Afforestation efforts doubled the forest cover in the area over the course of 15 years from 2001-2016.
The leading motivation for this large-scale afforestation is to combat “desertification” – the degradation of fertile land into desert. Desertification inhibits farming and raises the risk of flash flooding.
Desertification in China has chiefly been driven by large-scale deforestation. Cutting down trees causes soils to become loose and vulnerable to erosion. As soil erodes away, the land becomes infertile and desert-like. Replanting trees can help to re-anchor and restore soils.
Research estimates that, from 1973-2003, newly planted forests in China absorbed around 774m tonnes of carbon.
China plans to continue increasing forest coverage to 25% by 2035 and 42% by 2050. This effort includes participation of private companies as well; Alibaba and Alipay plan to invest $28 million in tree-planting projects.
Some scientists believe that afforestation should be seen as one of the most favourable options for removing CO2 from the atmosphere. Scientists have reasoned that, in order to limit impacts on agriculture and natural forests, afforestation should be primarily undertaken on low-quality pasture and grassland. This has been the Chinese approach. Research covered by Carbon Brief found that the global reversion of non-forest land to forests could offset around 253bn tonnes of CO2 between 2018-2100. This is equivalent to around seven years’ worth of global CO2 emissions at current levels.
Part 2 – Source: Carbon Brief, 09.10.2018