The rainforest ecosystem
Forests (taiga, temperate, subtropical and tropical) are differentiated between according to earth’s climatic zones, which are divided between the polar caps and the equator. The permanently humid inner tropics denote a ‘belt’ along the equator in which the most species-rich ecosystem on earth can be found. These tropical rainforests are located in Amazonia’s sprawling lowlands, the Congo Basin (Africa) and the low-lying South-East Asian islands.
Megadiversity in the tropical rainforests
Evergreen rainforests require high and consistent precipitation throughout the entire year. This amounts to a minimum of 2,000 mm per year and 100 mm per month. It rains almost every day in the tropical rainforests. While temperatures hover between 25ºC and 28ºC all year round, the daytime temperatures can in fact fluctuate between 20ºC and 38ºC. Unlike at other latitudes, there are no seasons along the equator, meaning that one often speaks of diurnal cycles instead. The rainforest climate is characterised by high air humidity. The combination of all these factors leads to development of the most biologically-diverse animal and plant world on our planet.
Because the floors of most rainforests are very thin and poor in nutrients, there is vast biological diversity. Most nutrients are stored in the plants and roots. When these die, they are rapidly reabsorbed into the nutrient cycle. Some of the plants and animals have developed an extremely refined survival strategy, primarily with regard to the use of light. One often speaks of “megadiversity centres” and “biodiversity hot spots” when discussing the tropical rainforests. Three out of four of the 1.85 million species known to date originate from the tropics, but not all have yet been added to the register and analysed.
The Amazonian ecosystem’s optimal climatic conditions have led to a high diversity of species. Alone 45,000 species of flora have their home here, and 500 types of trees and over 93,000 individual plants can be found on a surface area of 200 square kilometres. Very different adaptation characteristics have been developed to make optimal use of the conditions. In the Amazon region, one speaks of a diurnal cycle – so that the difference between the daytime and night-time temperatures is greater than the difference between the coldest and warmest months of the year. In parts, one speaks of the ‘flood season and non-flood season’. The water levels can fluctuate by up to 15 m. Most trees stand up to their tips under water from time to time. Different types of rainforests have evolved from these conditions, each of which has adapted to its respective conditions. A distinction is primarily made between the Terra firme (classic tropical evergreen lowland rainforest), the campina forests (mainly nutrient-poor soils), and the Várzea and Igapó (tropical evergreen flooded forests). The diversity of trees is estimated at 3,000 species (Central European forests are home to around 50 species of trees).
A further significant factor in plants’ development is the ‘fight for light’. Plants on the floor of the primeval forest receive just 2-3% of the daylight, but have developed strategies to make optimal use of this.
Changes in the Global Value of Ecosystem Services
The new paper, published in Global Environmental Change, builds on a 1997 study published in Nature on the global value of ecosystem services, and estimates the changes since then. This paper updates the unit value estimates and creates the first estimates of changes in global ecosystem services value (between 1997 and 2011) in monetary units.
“Our estimates show that global land use changes between 1997 and 2011 have resulted in a loss of ecosystem services of between $4.3 and $20.2 trillion [per year], and we believe that these estimates are conservative,” the study states.
In 1997, the global value of ecosystem services was estimated to average $33 trillion/yr in 1995 $US ($46 trillion/yr in 2007 $US). In this paper, we provide an updated estimate based on updated unit ecosystem service values and land use change estimates between 1997 and 2011. We also address some of the critiques of the 1997 paper. Using the same methods as in the 1997 paper but with updated data, the estimate for the total global ecosystem services in 2011 is $125 trillion/yr (assuming updated unit values and changes to biome areas) and $145 trillion/yr (assuming only unit values changed), both in 2007 $US. From this we estimated the loss of eco-services from 1997 to 2011 due to land use change at $4.3–20.2 trillion/yr, depending on which unit values are used. Global estimates expressed in monetary accounting units, such as this, are useful to highlight the magnitude of eco-services, but have no specific decision-making context. However, the underlying data and models can be applied at multiple scales to assess changes resulting from various scenarios and policies. We emphasize that valuation of eco-services (in whatever units) is not the same as commodification or privatization. Many eco-services are best considered public goods or common pool resources, so conventional markets are often not the best institutional frameworks to manage them. However, these services must be (and are being) valued, and we need new, common asset institutions to better take these values into account.