Presidential Address 2015: Biodiversity conservation: moving towards ecosystem services
Prof. Wipula Bandara Yapa
President – Institute of Biology
Department of Zoology, University of Colombo
Human Population Explosion and its impacts
The world has changed dramatically and in fact will continue to change melodramatically. We no longer live in a world that we lived in 20 years ago. Today, in the modern world, humans are intensely altering our ecological life support system and the natural environment has been altered to the extent that all living beings including the man himself are facing countless problems. Global human population growth amounts to around 75 million annually, or 1.1% per year. The global population has grown from 1 billion in 1800 to 7 billion in 2012. It is expected to keep growing, where estimates have put the total population at 8.4 billion by mid-2030, and 9.6 billion by mid-2050. It is fair to state that no other species that inhabited this planet underwent such a population explosion within such a short time.
These growing populations all over the world need shelter, food and other amenities, in fact, on a much larger scale than any other species living on earth. Each person uses far more land than the few feet they actually occupy. We use cropland to grow food, grazing land for meat and dairy, and oceans for fishing. We alter the land for habitation, agriculture, transportation, power generation and commerce. An average citizen in a developed country (European or American), owing to this luxurious lifestyle, needs 10-20 acres to supplement his needs. Our planet’s ability to provide an accommodating environment for human wants (rather than needs) is being diminished continuously. This unrelenting growth of human population and overutilization of vast amount of resources by a single species has caused detrimental impact on natural resources. We have replaced natural forest with monocultures, polluted air and water bodies and exploited natural resources irresponsibly. Consequently, scientists claim that our species has caused 322 animal extinctions over the past 500 years, with two-thirds of them occurring in the last two centuries. It has been estimated that animals extinct 100 to 1,000 times (some scientists even claim 1,000 to 10,000 times) faster than at the normal extinction rate, which is about 10 to 25 species per year. If this trend continues many researchers warn that we are in the middle of a mass extinction even faster than the Cretaceous-Tertiary extinction which wiped out the dinosaurs.
Unlike the previous mass extinctions, the next extinction could be due to the actions of a single species, us humans. Although some may argue this is implausible, we only have to look at the numbers of animals that are extinct or threatened by our actions. It has been estimated that about 17,000 species are threatened with extinction in the foreseeable future. These include not only some unknown invertebrates, but also familiar species such as the Polar Bear, Hippopotamus, sharks, freshwater fish and Mediterranean flowers. Marine species are proving to be just as much at risk as their land-based counterparts.
Sri Lankan situation
Sri Lanka, with a total land area of 65,610 km2 is a tropical island situated in the Indian Ocean. The tropical climate, with evergreen natural forests supports a vast biological diversity in the island andis designated as one of the world’s biodiversity hotspots. Sri Lanka has greater biodiversity per unit area than any other country in Asia. When the biological diversity of 8 Asian countries (Sri Lanka, Malaysia, Vietnam, Philippines, Thailand, Myanmar, Indonesia, India) is compared and ranked according to the average number of species per 10,000 m2, Sri Lanka has the highest number of species in mammals, amphibians, reptiles and flowering plants. As elsewhere in the world, Sri Lankan biodiversity is also threatened by the anthropogenic activities.
Along with the increase of the human population, the forestcover which had been approximately 80% of the total land area has now decreased to about 30% and the percentage of closed-canopy natural forest areas is 24%. Between 1956 and 1983 the natural forest cover of Sri Lanka fell from 2.9m ha to 1.75m ha. If this reduction continues at this rate, all natural forests will be gone by the year 2030. The loss of natural forests in Sri Lanka is directly related to the increasing human population. The human population that had been 2.3 million in 1870 has increased to 20.3 million in 2012. Natural forests in Sri Lanka has been cleared by colonial rulers for agriculture, mainly for tea and rubber. In the recent past, ambitious development projects such as accelerated Mahaweli scheme and recent agricultural projects such as Pelwatte Sugar Industries resulted in massive scale deforestation in the island. Mature and well-established forest plantations cover an area of about 72,340 ha (only 1.1 % of the total land area of the country). Out of this approximately, 15,600 ha is under Conifers, 8,400 ha is under Eucalyptus, and about 33,000 ha is under Teak plantations. In addition to the above, fuelwood plantations also occupy over 13,000 ha.
These natural forests are the home and breeding, foraging and roosting habitats of the fauna of Sri Lanka. The rapid loss of the natural forests in Sri Lanka had drastic in fact on most of animal species. According to 2012 IUCN report, five species of plants and 18 species of Amphibians have not been recorded in last 100 years or already extinct. Another 18 species of fish, 42 species of amphibians, 42 species of reptiles, 8 species of birds and 11 species of mammals are categorised as critically endangered.
Sri Lankan Bats
The threat to our wildlife can be best illustrated by taking the population changes that have taken place in Bats. Sri Lanka was endowed with a very rich resource of bats, with 30 species. In fact Chiropterans are the largest order of mammals and bats comprise about 1/3 of mammals in Sri Lanka. Their status had been drastically changed in the recent past. Our studies since 1986 to date have shown that bats are one of the highest endangered species in Sri Lanka. Several species that had been described as common 100 years back are in fact rare or not been recorded since then. Four species of bats (Tadarida aegyptiaca, Chaerephon plicatus, Falsistrellus affinis and Scotophilus kuhli) have not been recorded after the survey by Phillips in 1933. About five species of bats (Scotophilus heathii, Kerivoula hardwickei, Hesperoptenustickelli and Saccolaimus saccolaimus) have been recorded either only once or twice. The alarming factor is that the population sizes of even some common species are decreasing drastically. For example, in a survey carried out by Ruebsamen and coworkers, six species of cave dwelling bats have been recorded in 18 locations. When these roosts were revisited 7 years later, bats have disappeared from 8 locations. This threat to bats is still continuing, perhaps on a larger magnitude. During a survey of Sri Lankan bats carried out by us between 1995 – 2000, it was noted that bats have disappeared from 17 locations, when the observed sites were re-examined at the end of the study. Our observations have shown that bats are under constant threat of direct and indirect actions of humans. Deforestations, destructions and disturbance in the roosting sites, as well as illegal hunting pose direct threat to the survival of bats. Caves are often visited by hunters and large numbers of trapped bats can be easily killed.
Valuing Nature – Ecosystem Services
Biodiversity plays an important role in ecosystem function and in the many services that ecosystems provide. Some of these include nutrient and water cycling, soil formation and retention, resistance against invasive species, plant pollination, climate regulation, and pest and pollution control. Escalating biodiversity loss in any country will definitely have serious implications for human wellbeing and sustenance. Unfortunately, we have failed to realise this immense monetary value of the biodiversity, which probably is one reason for our failure to conserve biodiversity in Sri Lanka.
It is estimated that the monetary value of goods and services provided by ecosystems amounts to about 33 trillion dollars per year. An estimated 50,000-70,000 plant species are used in traditional and modern medicine worldwide. About 100 million metric tons of aquatic organisms, including fish, molluscs and crustaceans are taken from the wild every year and represent a vital contribution to world food security.
Insects are often considered as pests. Although some insects are pests and some are harmful, a large number of insects such as bees, wasps, butterflies, moths, hoverflies and beetles are extremely important for our survival. The estimated annual value of the ecological services provided by these insects in the United States alone is approximately $57 billion. Many plants depend on insects for pollination. The value of crop production from pollination by native insects is estimated to be about $3 billion in the USA alone. The role played by bats (and many other species of wildlife) in maintaining a healthy environment and their immense economic potential had never been properly appreciated. Insectivorous bats may eat up to 80-100% of their body mass in insects on a nightly basis. A study carried out in the cotton dominated agroecosystems of southern Texas, USA, has shown that the contribution of bats to be $12-$173 per acre each year. By extrapolating these figures to the whole country, it has been estimated that economic contribution to the USA’s agroecosystems to be between $3.7 and $53 billion/year. Fruit bats are known to pollinate over 500 plant species including mango, banana, cocoa, durian, guava and agave (used to make tequila). Some species of bats play a critical role in spreading the seeds of trees and other plants. Tropical fruit bats often carry seeds to a feeding site and then excrete the seeds far away from the original tree. Our studies in Sri Lanka , carried out in two natural caves (Wavulgalge and Wavulpena cave) have shown that, insectivorous bat species in Sri Lanka, consume prey up to 30% of their body weight as determined by the weight difference before and after foraging. Our calculation showed that bat populations in these two caves consume over 1168 kg of insect prey each night. Thus, the weight of the insects consumed by these two cave population in a year is estimated to be 426,420kg. The diet of these bats includes variety of insect prey from 15 insect orders. We generally value those ecosystems and species we find useful or of interest to us, but we also have to recognize that other living beings have value aside from their utility. Each species (plant as well as animal) has a place in nature and has the right to survive. As humans, we have larger control over their existence. If we wish to, we can keep our population at sustainable levels and live in harmony with other species. If we do not appreciate the role played by other living beingsand continue to disregard the right of other animals to share this planet with us, many species will soon disappear from this planet. If so, our descendants will not see the stars at night, will not experience wilderness and the incredible beauty of natural world.