ABSTRACT
Tropical forests provide a wide range of services which sustain life, such as timber and non-wood forest products (e.g. wild food), climate regulation, soil retention, water regulation and supply, pollination, landscape aesthetics and genetic information yet to be discovered. They also provide habitats for a vast store of species. At the global scale, tropical forests are home to about half of all existing animal and plant species on the planet, although they cover just about 7 per cent of the land. These forests show in fact the highest species richness compared to other forest ecosystems (Gibson et al. 2011; Whitmore 1998; Gentry 1992). In Central America there are approximately 22 million hectares of forests (FAO
2005), which adds up to 0.6 per cent of the global forest area. However, it is the region with the highest deforestation rate. As a matter of fact, in the period 2000-2005, around 285,000 hectares have been lost each year (FAO 2005), corresponding to a 1.3 per cent yearly loss in forest surface. Recent trends over the last decade indicate, however, a reduction in the deforestation rate in some tropical regions, especially in the Brazilian Amazon (IPCC 2014). Land-use change, deforestation and forest fires are considered principal causes for loss of forest cover in the Amazon, even more important than climate change (Settele et al. 2014). Nevertheless, the on-going degradation of forests throughout the Central American regions continues undebated with increasing fragmentation of human dominated landscapes on the Pacific slopes, and agricultural expansion into pristine Caribbean lowland forests. Conversion of pristine forests to other land uses has shown a significant decline in biodiversity levels, due to logging and agricultural activities which have expanded largely in the twentieth century. In addition to this loss, there is an increased vulnerability of species in the residual fragments of forest which might lead to their extinction.What is the impact of this fragmentation and the resultant loss in the functional capacity of these landscapes is a question that still needs to be answered. Degradation of large tracts on forests results in disruption of water supplies, deterioration of water quality (as the forest will no longer be able to filter and purify water), increased soil erosion (leading to
a higher frequency of landslides and the silting up of rivers), increased droughts in some places and flooding in others. Protecting the remaining tropical forest becomes a key factor in a context of global warming for many reasons. While the destruction of forests contributes to greenhouse gas emissions, healthy forest ecosystems provide services which can help in the climate change mitigation (e.g. through carbon sequestration) and adaptation (e.g. through reduction in soil erosion and protection of ground water supply; see Chapter 8 for a discussion on ecosystem-based adaptation). Despite the uncertainties on the impacts that climate change might have on forest ecosystems, the role of forests in this context is undeniable. All in all, forest ecosystem services affect human wellbeing, including health,
although the links might be complex and difficult to assess due to the multifaceted temporal and spatial interlaces. Some services are more directly linked with human health such as water supply, provision of wild food, recreational and aesthetic values. The latter, for example, benefit human health in many aspects. Forests create opportunities for active lifestyle through recreational activities and therefore play a role in reducing problems such as obesity and cardiovascular diseases, while encouraging other healthy behaviors such as the consumption of healthy food. Aesthetic values promote the reduction of stress and psychological tensions, thus contributing to mental health. Other benefits directly linked with human health and wellbeing include the possibility of reducing socio-economic health inequalities, improving air quality and microclimate, protecting water resources, obtaining pharmaceutical products and medicinal herbs, as well as improving community cohesion (Natural England 2009). Services such as soil retention or climate regulation are also linked with human health, although indirectly, as they provide a healthy environment for human beings and opportunities for climate change mitigation and adaptation. Degradation of tropical forests triggered by land use changes can have,
therefore, significant impacts on human health, not only for the loss of the above mentioned services, but also through other patterns, such as infectious disease outbreaks, or loss of habitats for animal species compelled to find other environments neighboring human infrastructures (ForHealth 2014; IUFRO undated). In these conditions, climate change would be an additional stressor which might exacerbate these impacts. Forests are certainly very receptive to changes in climate conditions. Climate factors such as temperature, solar radiation, rainfall and CO2 influence strongly forest productivity and their functioning. On the other side, forests sequester large quantities of carbon from the atmosphere, they provide a cooling effect through evapotranspiration and clouds, thus contributing to control climate change. It is estimated that 40 per cent of carbon worldwide is stocked in tropical forests, which show also high sequestration rate of CO2, while also contributing to more than half of gross primary production (Pan et al. 2011). As for the expected impacts of climate change, the last IPCC assessment
predicts (with medium confidence) that in the low mitigation scenarios there is a high risk of irreversible alterations in the functioning and composition of forests and other terrestrial ecosystems, with consequent modifications of vegetation types
and losses of forests especially in the Amazon and the Arctic (IPCC 2014). These changes are likely to be associated with a shift and alteration in habitats which will occur much more rapidly than the natural migration, triggering a change in plant and animal species, as well as increasing the risk of their extinction. In addition, these changes in forest composition, accompanied by degradation and deforestation, are expected to produce a great loss of carbon which will be released into the atmosphere, while the standing biomass will decrease due to the increased frequency of outbreaks, pests and forest fires. Forest fires will increase (with high confidence) due to the increased risk of droughts and because of land use changes, especially in moist tropical forests where there is higher vulnerability to droughts. Dry tropical forests in Central and South America, which have already seen a dramatic reduction due to human activities, are expected to face an increase in temperature and a decrease in precipitation patterns. These changes might increase the risk of degradation and replacement in dry tropical forests (Miles et al. 2006), though there is a low confidence in these predictions. Lastly, increased forest dieback in tropical regions are expected over the twenty-first century (with medium confidence), associated with higher temperatures and droughts, which can lead to further reductions in species diversity and spread of invasive species, while influencing the forest composition in terms of species and structure (IPCC 2014; Anderegg et al. 2012), with additional risks for carbon storage, timber production and water quality. As a consequence of the mentioned changes, many ecosystem services provided
by tropical forests will be under threat. Regarding biomass and soil carbon, although these are currently showing an increase in terrestrial ecosystems (including in the Amazon), they are highly vulnerable due to the rise in temperature, droughts and fire episodes expected for the twenty-first century (IPCC 2014). As for primary production, an increase is predicted by IPCC in terrestrial ecosystems compared with the pre-industrial era (low confidence; IPCC 2014). Trends in timber production are different according to the geographical area considered, though a general future trend of increase in forest production is expected with climate change (IPCC 2014; Kirilenko and Sedjo 2007). However, the effect cannot be clearly attributed to climate change alone, due to many other confounding factors in forest management. Increased forest dieback might decrease timber productivity in tropical regions. Other important changes relate to habitat shifts and alteration of their quality,
with risk of extinction and impacts on species abundance; increase in pest species and diseases which will affect forest productivity, and expected decline in pollination caused by a reduction in insect abundance, with effects on plant reproduction. Still, water availability is expected to be one of the most affected services in
forests, with higher risks of flooding and droughts (Settele et al. 2014; Kundzewicz et al. 2007).The effects of climate change on freshwater systems will exacerbate many forms of water pollution, and will impact on water system reliability and operating costs. Of all ecosystems, freshwater systems will have the highest proportion of species threatened with extinction due to climate change (MEA
2005), via the warming of water, flow alteration and loss of aquatic habitat (for instance, due to ice-jam flooding or decrease on river discharges). Considering that Central and South America are highly dependent on water
resources for the agricultural and hydropower sectors, significant impacts can be expected in this respect (IPCC 2014). In the case of hydropower, the loss of forest area might cause, in a first instance, a reduction of evapotranspiration, which would, on the one hand, increase water flows and affect positively energy production. On the other hand, however, it would influence the rainfall system which is sustained by the forest itself, reducing in this way the quantity of water flows as well as the water quality (e.g. sedimentation problems) for hydropower, so that these two effects have to be considered jointly when modelling the impacts (Stickler et al. 2013). The expected changes in the provision of ecosystem services will affect human
wellbeing and welfare in many respects. As already mentioned, there is an impact on human health (directly or indirectly affected), which can be subsequently translated into economic costs for the public health, in addition to other tangible and intangible costs for the population in terms of loss of productivity and leisure time, suffering and quality of life. More tangible impacts are expected for specific economic sectors, such as tourism, agriculture and hydropower production, for the high potential they represent in many regions located in tropical forests. The expected reduction in the provision of cultural services, water supply and regulation, will inevitably translate into economic losses which will be reflected in national economies. Further consequences are envisaged for forest-dependent groups and indigenous populations, though their monetization might pose some problems in the quantification. Many of the impacts on ecosystem services mentioned above can be valued in
monetary terms, as it is discussed later in the chapter, through market and nonmarket valuation methods. For some of them, the conversion into an economic unit becomes more difficult due to the nature of the service itself, as is the case for ecosystem services which are not directly traded in the market (e.g. water regulation, recreational activities, forest habitats). Despite these difficulties, the need for monetary values is undeniable in a policy context, where decisions have to be made about the use of natural resources and the adoption of appropriate mitigation and adaptation measures. Among the mitigation options, forest restoration and sustainable forest management can help in the general mitigation effort, while improving local economies and reducing poverty. Sustainable forest management (e.g. reduction of logging, prevention of fire, agro-forestry practices) can be also seen as a key measure for adaptation as it increases resilience of tropical forests. However, the decision to set up mitigation and adaptation plans relies necessarily on the knowledge about their economic costs and the flow of benefits they can generate in the short and long term. The economic valuation of ecosystem services represents, therefore, the cornerstone for applying cost-benefit analysis in decision-making processes. The present chapter discusses the importance of ecosystem services provided by
tropical forests, their utility for human wellbeing and how their value can be
translated into economic units. The following section introduces briefly the principal ecosystem services supplied by tropical forests, while contextualizing their importance in Central America. Problems derived from the ecosystem services classification are discussed in this section as well. I then analyze the benefits provided by ecosystem services to human wellbeing and the types of values associated with these benefits. I examine the main challenges in economic valuation, its implications in the long-term and the existing trade-offs in the monetization of ecosystem services. An overview of the main methodological approaches for economic valuation is provided in the penultimate section, where limitations and drawbacks are also examined. Finally, some concluding remarks are presented.
