More often than not, environmental sustainability is seen in terms of the quantum of human activities vis-à-vis the potential carrying capacity of the planet earth. The technological innovations and possibilities may suggest expanding bounds for a sustainable future. However techno savvy societies seem to ignore the fact that the proper functioning of ecosystems with the mutual interdependencies of their services, ecosystem services, is crucial for survival of humanity.
Although people are generally aware of the ecosystems that make up the human habitat, ecosystem services as a concept is recent and refers to ‘the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfil human life’ (Daily, 1997). The entire planet can be seen as a vast network of integrated ecosystems and ecosystem services may range from global to microscopic in scale.
If we were to talk about the connections, ecosystems are one web of inter-connected services: plants inhale carbon dioxide and produce oxygen; organisms decompose and detoxify detritus; species help in soil formation so essential for cultivation – recycle the nutrients essential to agriculture; thousands of animal species pollinate and fertilize plants, protect them from pests, and disperse their seeds. In nutshell, the ecosystems recreate and sustain themselves.
There are, however, internal threats to ecosystem services. A case in point is habitat fragmentation which has a serious effect on plant reproduction. In the tropical dry evergreen forests of the Coromandel Coast of southern India, the reproduction of plants was severely affected due to paucity of pollinators, called ‘pollinator limitation of fruit set’. Self-incompatible species that were predominantly outcrossing suffered higher levels of pollinator limitation. In fact these species had lower densities of seedlings and saplings indicating that pollinator limitation affect their ecological success. In such cases small patches of forest might be functionally extinct and there has to be a concerted effort to rehabilitate the pollinator fauna. Another problem is the population size of plants. Few, far apart individuals suffer reproductive loss as a result of ineffective pollination. Therefore in any forest restoration effort the number of individuals of each species and their density is also important. If the plantings are at low density, the plants might not be able to reproduce since pollinators would find it difficult to move pollen between dispersed individuals. Inbreeding becomes another issue. Plants are like all of us, they need to survive, grow and find mates.
Most terrestrial carbon storage occurs in forest trees. However, as pointed out by Sekercioglu (2010), the global carbon cycle has been disturbed by about 13 per cent compared to the pre-industrial era. Given the dominance of carbon in shaping life and in regulating climate, this perturbation has already been enough to lead to significant climate change with worse likely to come in the future (Intergovernmental Panel on Climate Change (IPCC), 2007).
When humans alter ecosystems, large mammals are typically the first species to disappear. The ecological and economic consequences of losing large mammal populations vary depending on the location and the ecological role of the species lost. The loss of carnivores has induced trophic cascades: in the absence of top predators, herbivores multiply and deplete the plants, which in turn drives down the density and the diversity of other species (Ripple and Beschta, 2006). Losing large herbivores and their predators can have the opposite effect, releasing plants and producing compensatory increases in the populations of smaller herbivores e.g. rodents (Keesing, 2000) and their predators e.g. snakes (McCauley et al., 2006). Such increases, while not necessarily detrimental themselves, can have unpleasant consequences.
Many species depend on the activities of a particular large mammal species. Certain trees produce large fruits and seeds apparently adapted for dispersal by large browsers (Guimarães et al., 2008). Defecation by large mammals deposits these seeds and provides food for many dung beetles with varying degrees of specialisation. In East Africa, the disturbance caused by browsing elephants creates habitat for tree dwelling lizards (Pringle, 2008), while the total loss of large herbivores dramatically altered the character of an ant-plant symbiosis via a complex string of species interactions (Palmer et al., 2008). These examples and others suggest that the loss of large mammals may precipitate extinctions of other taxa and the relationships among them, thus decreasing the diversity of both species and interactions. Conversely, protecting the big areas needed to conserve large mammals may often serve to conserve the greater diversity of smaller organisms – the so called umbrella effect. In an interactive manner, the more complex an ecosystem is, the more is the biodiversity with a consequent increase in ecosystem functions.
Even with these few examples, the importance of ecosystem services become amply clear for the well being of people at large. How to implement the concept is an issue which requires skilful attention by experts from disciplines as varied as biology and physical sciences on one hand to social sciences on the other. Apart from new programmes and institutions that need to be created for environmental accounting, i.e., value of ecosystem services, political will and policy openness are crucial. Good tools are ineffective in the absence of effective implementations. A more difficult goal is convincing the private and public sectors to incorporate ecosystem services into their decision making processes (Daily et al., 2008, quoted in Sekercioglu, 2010). As natural disasters like earthquakes, tsunamis and hurricanes become more severe in their impact, the voices of concern for the environment and its intricate functioning are gaining prominence.