Forests are of the most important terrestrial ecosystems and an integral component of the Earth system. They are habitat and/or livelihood for a quarter of the world population. At the same time, forests (particularly tropical forests) are the most biodiverse habitats of our planet: two thirds of all animal and plant species live in forests.
In spite of their importance, today, forests are more than ever before under the threat of a growing world population and climate change. Mankind has already destroyed more than half of the forests. A large part of the remaining forests is disturbed. Only a third of the global forest area consists of primary forest. A large part of that is regarded as being seriously endangered. Driven by the expansion of agriculture and increasing wood use, a further 10 to 15 million hectares of forest are destroyed every year, due to conversion into agricultural land, forest clearance or illegal logging. This damage not only destroys important resources and the habitat of many plants and animals, but it also releases a large amount of CO2.
Consistent global monitoring of the condition of the forests and the influence due to human activity and climate therefore becomes an urgent necessity. The lack of suitable remote sensing systems with the ability to estimate the vertical structure of forests and its spatial variability makes accurate monitoring of the disturbed and degraded forests impossible. Hence, the degree of forest disturbance and the ecological consequences remain unknown.
Tandem-L will allow for the first time to map the vertical forest structure and to monitor seasonal and annual variations globally with high resolution. This will enable to map for the first time the (vertical) complexity and diversity of Earth's forest ecosystems and to assess the extent and intensity of forest structural disturbances.