3. Provisioning services

of the world forest land is covered with productive forest plantations. However, this area

All forest regions (tropical, subtropical, temperate, sub-boreal, and boreal) are being affected by land use change processes. In particular, tropical forests have suffered from the biggest changes (both positive and negative) of all the forest types although the loss rate is still 3.6 times bigger than the rate of surface gain [6]. These authors estimated that losses in tropical forests area accounted for 32% of total forest loss in the world, with half of those losses being concentrated in South American tropical forests. However, there are big differences among tropical countries in rates of loss and gain of forest area. For example, Brazil has recently shown a decline in annual forest area loss, moving from a high of over 40,000 km<sup>2</sup> year−<sup>1</sup> in 2004 to a low of under 20,000 km<sup>2</sup> year−<sup>1</sup> in 2011. On the other side, for the same period Indonesia has gone from losing 10,000 km2 year−<sup>1</sup> in 2003 to over 20,000 km<sup>2</sup> year−<sup>1</sup> in 2012. In addition, subtropical forests are experiencing important land use change, with many planted forests being usually treated as crops, causing that old-growth natural forests to be relatively rare in these biomes [7]. As a result, although the absolute losses in surface are not as big as in the tropics, subtropical forests have experienced the largest relative changes in forest

Tropical forests have been extensively disturbed by human beings since long time, and the intensity and extent of disturbance will continue into the future [8]. Land use change in the tropics is caused mainly for agricultural use [9]. Land use change will affect ecosystem services, and climate change makes this a more complicated but emergent problem for human beings [10]. Many land use practices still widely extended in tropical forests (e.g., fuel-wood collection, forest grazing, and road expansion) can degrade forest ecosystem conditions—in terms of productivity, biomass, stand structure, and species composition—even without changing forest area. Changing the way the land is used also paves the way for the introduction of invasive species, including pests and pathogens that can degrade the original forests. Another major change is the alteration of fire regimes, by modifying fuel loads, removing coarse woody debris, increasing the number and frequency of ignition sources, and even modifying the local meteorological conditions [11]. On the other hand, human activity can also improve forest conditions, either by direct forest management or by unintended effects of other processes, such as increased nitrogen deposition, atmospheric concentrations of CO2, and peatland drainage. Such processes have caused the increase in standing biomass of European forests by 40% between 1950 and 1990, while their area remained largely unchanged, accelerating forest growth in the twentieth century [12]. These forests have become a substantial sink of atmospheric carbon [13], although other ecosystem

services including those provided by peatlands and biodiversity are likely diminished.

All kinds of ecosystem services rely on the interplay of the organisms and the abiotic environmental factors of the ecosystems. Therefore, biodiversity of an ecosystem is the key property behind ecosystem services. Globally, the biodiversity is decreasing mainly due to the anthropogenic interferences [14]. Land use change has its first and direct impact on the land surface with the modification or removal of current organisms and thus will change the biodiversity to

expanded by 2 million ha annually in the 1990s and by 2.8 million ha in the 2000s [5].

2 Tropical Forests - The Challenges of Maintaining Ecosystem Services while Managing the Landscape

cover losses and the smallest relative gains [6].

2. Land use change and biodiversity

Tropical forests maintain a high variety of plants, animals and microbes, and therefore many different species suitable for human consumption. In addition, to be a genetic reservoir for potential food sources [23], tropical forests can provide enough food to maintain the human population of traditional habitants [24], reaching values up to US \$18.5 per hectare and year [25]. Fuelwood is also the main energy source for heating and cooking of millions of people in tropical countries. For example, in Mexico alone, 7 million of rural people depend on tropical forests [26]. Timber, usually of high quality and value, is among the most valued goods provided by tropical forests, sometimes being also the cause of the deforestation (often illegal) and land use change [27]. Similarly, traditional medicine from tropical communities is also providing new compounds for medicines, but at the same time can also cause local extinctions if their harvest is not controlled [25].

Among other goods, water is usually given from granted, but freshwater is a very valuable ecosystem service that comes mainly from higher elevation ecosystems. Ponette-González et al. [28] performed a meta-analysis of the effects of land use change on hydrological cycles of tropical high-elevation ecosystems. The types of land use change included the conversions from forest to grassland, agroforest to nonforest, nonforest to tree plantation, and recent glacier retreat. The deforestation did not lead to an expected substantial increase in downstream runoff in Latin America and the Caribbean and in Hawaii. On the other hand, Muñoz-Villers and McDonnell [29] compared the streamflow of three watersheds that have old-growth cloud forest, 20-year-old regenerated cloud forest, and heavily grazed pasture, respectively, in Mexico. The land use type of pasture produced 10% higher streamflow compared to the two forested catchments. Their results imply that a short period of 20 years of recovery from pasture to forest may be enough for the restoration of hydrological conditions.
