Afforestation in which means forestry planting trees or the sowing of seeds , with the aim of forestation often referred to as restoration of a previous through deforestation or storm damage disappeared forestation. If the area to be reforested was previously planted with forest , one speaks of reforestation , otherwise it is called first afforestation .
The first historically documented successful method of reforestation with coniferous seeds on a large scale, developed in 1368 the Nuremberg council and Trade Mr. Peter Stromer (around 1315-1388) in Nuremberg Reich Forest . This made this forest area the world's first artificial forest and Stromer the “father of forest culture ”. In Germany, reforestation of deforested or damaged forest areas is mandatory according to Federal Forest Act .
A law was passed in the Philippines in 2019 requiring every elementary school, high school and college student to plant ten trees before graduation.
On September 14, 2019, a charity program on reforestation was broadcast on TV 2 . Donations were received for 914,233 trees. According to the organizers, this was the first program of its kind worldwide for climate protection .
The hoped-for effect of afforestation varies from region to region and time. As a rule, all of these forest functions should be achieved through afforestation activities.
- Reduction of soil erosion by wind and water, preservation of the fertility of surrounding agricultural areas ( China's Green Wall , Dust Bowl in the American Midwest)
- Increase in groundwater mirror
- Protection of groundwater catchment areas
- Restoration of biodiversity
- Stopping an impending desertification
- Prevention of flooding due to the high water storage capacity of the forest
- Protection against avalanches in mountain regions
- Wood recycling or recovery of the fruits , leaves, etc.
- Binding and storage of CO 2 for climate protection
In reality, however, the goals can conflict. It has been shown that in the world's largest reforestation program on the semi-arid north Chinese loess plateau with the tree species Robinia, although the increase in biomass and the reduction of erosion could be achieved as planned, the rate of groundwater recharge under the forest unexpectedly fell sharply due to increased evapotranspiration , as a result of which there was a local water shortage.
Implementation and impact
In the case of ecological afforestation, a distinction is made between the methods of forest sowing and forest planting . In the case of a forest sowing , seedlings are set that are usually well rooted from the start. In the case of forest planting, trees that have already grown are planted, the roots of which are often damaged and deformed by the transplanting. As a result, the trees have less support and growth is also impaired. Twelve years of root research by the Bavarian State Institute for Forest and Forestry (LWF) showed that only 19% of all planted trees examined showed no root deformation, while 69% of the rejuvenated and sown trees had perfect roots. Plant shocks that result from differences in the nature of the soil in the nursery and the area to be planted can also ultimately cause a small tree or cutting to die. Known plant densities are between 400 trees per hectare for a tree garden and 1,000 trees per hectare for a commercial forest. In the pine forests of the GDR , planting densities of 10,000 trees per hectare were also common.
Young trees can benefit from an older tree or older tree population through shading and microorganisms in the root network. Fast -growing alders are used as so-called nurse trees for oaks .
Bamboo forests in monoculture often form impenetrable walls for larger living beings and accordingly offer little habitat for flora and fauna. It is advisable to create firebreaks to fight fires and pests right from the start. These aisles are also used for irrigation during drought or as a transport route for timber harvesting .
In dry areas, the saplings are washed ashore not only with a watering can, but also with complex hose irrigation systems or alternatively the use of gel sausages . These sausages consist of 98% water, which is converted into a dry gel consistency on the surface with the help of cellulose and aluminum sulfate and enables controlled, low-evaporation irrigation of the young trees, whereby the enzyme cellulase , which occurs in soil bacteria, causes a breakdown of the dry-water gelwurst Plays a key role.
Fast-growing trees have a higher water requirement than slow-growing trees, and so it can happen that a newly planted forest with thirsty trees simply drains the surrounding arable land. However, this serious problem can be mitigated or even avoided through a skilful selection of trees and possibly a reduced planting density.
The reforestation of tropical rainforests, which is oriented towards the primary forest , is practically done by recombining tree and shrub seeds found in collected animal excrement. The feces of monkeys and bats are particularly in demand, as they are generally known for their intensive consumption of forest fruits.
Reforesting deforested regions can be difficult. Sometimes only 0.5% of the trees that are planted survive. They lack nutrients and the microbes present in the forest floor . Mycorrhiza growing in and on the roots provide the young tree with water and nutrients . Different groups of bacteria prove to the growth of tree roots as helpful as some of the growth hormones secrete of trees similar materials, and phosphate solve and nitrogen fixing. A young tree finds this environment in an existing forest. Combining fertilizers and pesticides with the microbes fails as phosphate fertilizers work against some bacteria and fungicides against mycorrhiza. An attempt to use the microbes on fruit trees resulted in faster growth and earlier, smaller and tastier fruit yields.
Attempts have been made to have trees planted by drones in order to combat deforestation.
Afforestation and climate change
Afforestation can only compensate for the use of fossil fuels if the carbon bound in the process does not get back into the atmosphere as CO 2 , neither through fire nor rot. Deposition requires repositories for similar amounts of carbon as extracted from the earth, in any modification or chemical combination.
How much carbon dioxide is bound in trees depends on the tree species, the age of the tree and other factors, so that general statements are difficult. As a rule of thumb, a 23-meter-high European beech tree with a trunk diameter of 30 cm at breast height binds around one ton of CO 2 in its organism. On average, it stores around 12.5 kg of CO 2 per year, with significant binding only taking place with advancing age.
In 2011, two Canadian scientists published a study on the effects of reforestation on the CO 2 content of the atmosphere. In their study, they came to the conclusion that afforestation would only counteract the global warming of the climate to a small extent, since dark forests have a relatively low reflectivity ( albedo ), i.e. they would only reflect little solar radiation. In the tropics, afforestation is three times more effective than in the temperate and high latitudes, since plants grow quickly there and therefore fix a lot of CO 2 .
For years, massive losses of forest areas have been observed, especially in the tropical forests of South America, Africa and Southeast Asia. This happens, for example, in Indonesia v. a. by replacing the original forest with oil palm plantations. In 2011 changes in land use such as E.g. the clearing of forests according to the IPCC releases approx. 0.9 ± 0.8 billion tons of pure carbon, which corresponds to about 10% of the total anthropogenic (“total anthropogenic”) carbon release. (For forest losses, see also the article on deforestation and the articles on forest fires 2019 in the boreal forests of the northern hemisphere and in the Amazon rainforest .)
According to research, older forests are more resilient to climate change than younger forests.
Controversy about the climate protection potential of afforestation
In 2019 a study by the ETH Zurich was published, according to which the earth could produce forests with 4.4 billion hectares, which is 1.6 billion hectares more than exist today. Assuming that 0.7 billion hectares are needed for the additional development of cities and agricultural areas, an additional 900 million hectares could be replanted worldwide. The study received considerable public attention, while scientists accused the authors of major errors in content and methodological deficiencies immediately after publication. In particular, the thesis of superiority over other climate protection measures aroused strong criticism from climate researchers. Other climate researchers such as Stefan Rahmstorf , Pep Canadell (Head of the Global Carbon Project ) and Myles Allen pointed out that this statement was based on a calculation error in the study, as it did not take into account that carbon dioxide - which was previously buffered - was not taken into account. is released, which significantly reduces the net effect.
Science then published several critical comments on the study within a few months. a. pointed to methodological errors, optimistic assumptions and ignored research results and explicitly denied the results of the study. For example, a comment in which Pep Canadell collaborated repeated the criticism he had previously expressed and referred to incorrect assumptions with regard to the carbon storage potential and the carbon cycle . In addition, regardless of the storage potential, afforestation could only delay global warming temporarily, since the only way by which the earth temperature can be stabilized at a given level in the long term is to reduce human carbon dioxide emissions to zero. The study greatly overestimated the potential of forest reforestation and did not provide a single evidence for the statement that the restoration of ecosystems is the most effective climate protection solution. This conclusion is "scientifically simply wrong and dangerously misleading". Another reply published in autumn 2019 came to the conclusion that the key premises and data of the ETH study were incorrect and that the authors had consequently overestimated the potential of afforestation for binding carbon dioxide by a factor of five. Among other things, the authors would have wrongly assumed that the soils in non-tree-covered ecosystems contained no organic carbon, although considerable amounts of organic carbon can be found in these ecosystems and, for example, certain American grasslands stored as much carbon per hectare in the soil as tropical forests do of biomass. A replica published in November came to the conclusion that the carbon sequestration of forests estimated in the study of 7.6 tonnes per year and hectare was at least a factor of 3.2 too high due to non-consideration of various factors and that the land requirement for the plan was therefore not 900 Million ha, but 2.88 billion ha. a. the remaining carbon budget has been overestimated, as has the area available for afforestation. Finally, the authors noted that, as much as they would like to welcome the study's central conclusion that restoring ecosystems is one of the most effective climate protection solutions, they would have to conclude that afforestation is not a panacea for climate change and requires an unrealistically large area. Afforestation is to be welcomed, but the key factor in protecting the climate is reducing emissions. Bastin et al. defended their study.
List of major reforestation programs
- China's Green Wall
- Africa's Green Wall in the Sahel
- Liman (desert grove)
- Forest of the German Lands
- Green Belt Movement
- Barrage vert
- Reforestation of Iceland
- Afforestation of Scotland (Trees for Life)
- Trees for the Future (Silver Spring, Maryland)
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- Afforestation measures in the European Union
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