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Fast facts by UNEP

Trees include the largest and longest living organisms on earth.
Millions of hectares and billions of trees have to be planted to stabilize soil and water resources and to meet fuel wood needs.
To make up for the loss of trees in the past decade, we would need to plant 130 million hectares (or 1.3 million km2), an as large as Malaysia, Sabah, Sarawak and Kalimantan put together.
Covering the equivalent of 130 million hectares would entail planting approximately 14 billion trees every year for 10 consecutive years. This would require each person to plant and care for at least two seedlings a year.
Rehabilitating tens of millions of hectares of degraded land and reforesting the Earth is necessary to restore and maintain the productivity of soil and water resources.
Expanding tree cover on denuded lands will reduce pressures on remaining primary forests, helping to preserve habitats and to safeguard the Earth’s biological diversity. It will also mitigate the building of atmospheric carbon dioxide.
Article 3.3 of the Kyoto Protocol specifically calls for the maintenance of forests by afforestation and reforestation, and by controlling deforestation.
Humans have contributed to carbon dioxide emissions in two ways: by burning fossil fuels and by converting forestlands to other uses.
Rainforests cover only 7 per cent of the land on earth but they contain nearly half of all the trees on earth. They generate about 40 per cent of the world’s oxygen.
In one year, an average tree inhales 12 kilograms (26 pounds) of CO2 and exhales enough oxygen for a family of four for a year.
One hectare of trees can absorb 6 tonnes of carbon dioxide a year.
A long haul flight will produce 3.75 tonnes of CO2. (or one tonne of carbon)
Agroforestry programmes make trees more accessible and spread their benefits more widely. Trees on farms often yield more biomass. Nitrogen-fixing trees planted in shelterbelts or interspersed with crops can enhance soil fertility, increase soil moisture and reduce erosion.
Agroforestry systems contribute simultaneously to buffering farmers against climate variability and to reducing atmospheric loads of greenhouse gases.
The World Agroforestry Centre (ICRAF) recommends the planting of deciduous trees where water scarcity is a problem. They consume less water than evergreens during critical periods of water shortage and compete less with crops. They shed their leaves between one to six months per year and adapt to long-term rainfall patterns. Deciduous species are suitable for semi-arid areas.
Deep roots anchor the tree and topsoil to deeper layers and increase the resistance to landslides and bank erosion under wet soil conditions. Horizontal roots bind soil and also reduce erosion.
Aspirin originally came from the bark of a willow tree. Quinine, the cure for malaria, comes from the bark of Cinchona trees.
The net forest loss per day is 20,000 hectares or the equivalent of an area twice the size of Paris. This adds up to 7.3 million hectares per year.
Trees are the largest on earth,
The longest living creature.
树木是地球上规模最大,
存活最久的生物。