Extinction: The great threat before us

by Patali CHAMPIKA RANAWAKA

The United Nations has declared 2010 as the World Biodiversity Year. Its primary objective is to increase the public awareness of conservation and restoration of biodiversity in the world. It is estimated that nearly 750 families of species and approximately 1.7 million of diverse species belonging to these families are living on this planet. However, it is very unfortunate to note that many of these species are endangered or faced with the threat of extinction.

Biodiversity

Generally development is defined as an ever growing cycle of economic production and consumption. Therefore, the yardstick with which development is measured is based on economic and monetary terms. At present, the GDP per-capita level of Sri Lanka is 2,200 US$ and its corresponding world rank is 119. If this yardstick is modified incorporating the Purchasing Power Parity (PPP), our GDP would be 5,000 US$ and out of 176 countries which possess reliable relevant data, our corresponding world rank would be 112.

In order to provide a better estimate of development, incorporating education and health as two additional parameters, the UNDP has calculated the Human Development Index (HDI), and it elevates us to the 99th rank in the world. Subsequently, our Ministry was able to formulate a new index incorporating GDP per-capita (PPP), health level, education level, income distribution and poverty level, pollution and resources base (ecological foot print and biodiversity). We termed it as Sustainable Human Development Index (SHDI) as it provides a better assessment and a wide picture on sustainability. This index (SHDI) ranks Sri Lanka 27th and USA 94th in the world.

This clearly proves the fact that development is a another relative concept and it is based on the yardstick with which it is measured and further, we would be ranked 23rd in the world if biodiversity is used as the yardstick to measure the development. So, if the per-capita GDP is used as the yardstick to measure development, we are living in a so-called third world country. However, if the yardstick is modified incorporating other parameters like emission of carbon dioxide or biodiversity, we are living in a first world country.

Biological Diversity, simply stated is the variety and variability among living organisms and the ecological complexes in which they occur and it has three major levels such as genetic, species and ecosystem. Species are the building blocks of ecosystems and ecosystems provide the life support systems for human beings.

Loss of biodiversity mainly means the loss or extinction of species. Extinction has been a fact of life since life first emerged from the primordial ages.

The present few million species are the modern day survivors of the estimated several billion species that have ever existed.

All past extinctions have occurred by natural processes such as the direct result of competition with superior species, or even if most represented an inevitable failure to meet the challenges of minor environmental changes. But many, if not most, extinctions are reactions to environmental challenges so severe and unpredictable such as volcanic eruptions, meteorite destructions and avalanches.

Currently, extinctions caused by human beings are decreasing the Earth’s biological diversity at an unprecedented rate. Conservation biologists estimate that species are presently becoming extinct at a rate at least 100 times the natural rate of background extinction. More than 31,000 plant and animal species are currently threatened with extinction.

Although extinction is a natural biological process, it can be accelerated greatly by human activities. What is important to consider is that humans are making species to go extinct versus the natural process of extinction is the rate at which humans cause extinctions which is considered unnatural.

Usually, as one species is naturally evolving out of existence another species is evolving as a replacement for that particular niche. Humans cause extinctions so quickly that nature does not have time to evolve something new to fill in the gap. Therefore, humans cause many gaps to occur in ecosystems which disrupt the functioning of biological processes that keep us all alive.

This is why biological diversity is so important. Diversity can buy time so that a replacement species can be evolved. Thus, it acts like a buffer so that the ecosystem does not respond to the gaps by immediately collapsing. If that occurred, the life support systems would quickly shut down and all of life would die.

The five major extinction episodes of life on earth can be exemplified by the changes through geological time in family diversity of marine vertebrates.(See Table 1)

Extinction rates are usually estimated indirectly from principles of biogeography. The number of species of a particular group of organisms in an island system increases approximately as the fourth root of the land area. Using the above relationship ultimate losses due to the destruction of rain forest in the new world tropical mainland can be projected. If the present level of forest removal continue, the stage will be set within a century for the inevitable loss of 12% of the 704 bird species in the Amazon basin and 15% of the 92,000 plant species in South and Central America.

In general, the tropical world is clearly headed towards an extreme reduction and fragmentation of tropical forests, which will be accompanied by a massive extinction of species. At the present time less than 7% of the forest are protected within parks and reserves globally and even these are vulnerable to political and economic pressures.

Many published sources indicate that about 1.7 million living species of all kinds of organisms have been described. Approximately 950,000 are insects, 53,000 are vertebrates and 250,000 are plants.

The remainder consists of a complex array of invertebrates, fungi, algae and micro organisms. Most systematizes agree that this picture is still very incomplete and that the number of species on earth is based on the described fauna and flora. The idea of entomologists and tree specialists is that the absolute numbers falls somewhere between 5 and 30 million.

Today threats to species and ecosystems are the greatest in recorded history. Virtually, all of them are caused by human mismanagement of biological resources, often stimulated by misguided economic policies and faulty institutions that enable the exploiters to avoid paying the full cost of their exploitation.

The marine fauna has been underestimated since many species traverse along continental boundaries.

The new Worlds Register of Marine Species contains about 122,500 validated marine species names. Leading experts independently estimate that about 230,000 marine species are known to science.

also believe there are three times as many unknown (unnamed) marine species as known, for a grand total on earth that could surpass 1 million.

A species becomes extinct when the last existing member of that species dies. Extinction therefore becomes a certainty when there are no surviving individuals that are able to reproduce and create a new generation.

A species may become functionally extinct when only a handful of individuals survive, which are unable to reproduce due to poor health, age, sparse distribution over a large range, a lack of individuals of both sexes (in sexually reproducing species), or other reasons. Functionally extinct species in modern times are the Baiji dolphin and the South China tiger.

Many extinct species have had profound effects on other species through their interactions. In themselves, these interactions or functions are an integral part of biodiversity.In Sri Lanka, 21 amphibian species have been listed as extinct in the 2007 National Red Data Book. Of these, two species have been re-discovered in 2009.

This may have been due principally since a thorough survey had not been conducted for some time. Despite the fact that exact numbers are not known for extinct flora and fauna (Jurassic, Miocene and Pleistocene faunal lists are available but not for the Holocene period) what is listed as Critically Endangered has the highest chance of becoming extinct in the wild if conservation measures are not conducted.(See Table 2)

The marine fauna of Sri Lanka has been the least studied. Therefore, only approximate numbers can be given.(See Table 3)

Considering the plant species in Sri Lanka 71 species is considered as extinct whilst one species is considered as being extinct in the wild. Of the 1099 plant species evaluated for the 2007 redlist 251 species is considered as being critically endangered of this, 163 species are endemic to Sri Lanka.

The Global List contains very few of Sri Lanka’s threatened species. This is principally since the total number of nationally threatened species has not yet been included in the global list. In general, globally, the Jurassic habitats and the Miocene marine environment have become extinct. In Sri Lanka too, fauna that were described from their fossils are no longer extant. But several species have sustained from the Pleistocene such as the Acavus species whose genus is endemic to Sri Lanka. Species that are critically endangered are linked to their habitats that are facing degradation. The swamp forest at Waturana and the flood plain villus of the Mahaweli are such habitats that are facing extinction.

The writer is the Minister of Environment and Natural Resources