Why we are losing biodiversity
The threats to Biodiversity
- Habitat loss through changes of land use in particular the conversion of natural ecosystems to cropland, continues to be the biggest direct cause of biodiversity loss. Already, more than half of the Earth’s 14 terrestrial biomes have had between 20% and 50% of their total area converted to cropland.
- Unsustainable use of ecosystems and over-exploitation of biodiversity continue to be major threats. Many species are used by humans to fulfill basic needs. Many species are in a state of decline because they are being used at unsustainable levels or are being harvested in such a way that threatens the ecosystems on which they depend. These declines are widespread.
- Climate change is projected to become a progressively more significant threat to biodiversity in the coming decades. Already, changes to the timing of flowering and migration patterns as well as to the distribution of species have been observed worldwide . In Europe, over the last forty years, the beginning of the growing season has advanced by 10 days on average . These types of changes can alter food chains and create mismatches within ecosystems where different species have evolved synchronized inter-dependence, for example between nesting and food availability.
- Plants, animals and micro-organisms transported deliberately or accidentally to an area outside their natural geographical ranges can cause great damage to native species by competing with them for food, eating them, spreading diseases, causing genetic changes through inter-breeding with native species or populations, and disrupting various aspects of the food web and the physical environment. More than 530 alien species with a demonstrated impact on biodiversity have been found across 57 countries for which data were collated, with an average of over 50 such species per country (and a range from nine to over 200)
- The accumulation of pollution such as phosphorus and nitrogen, largely from excess fertilizers running off farmland, and from sewage and other effluents, causes the build-up of algae able to benefit from the added nutrients. The algae themselves can be toxic and therefore create a health hazard, but the greatest damage to biodiversity is caused when they decompose and use up large quantities of oxygen in the water, creating “dead zones” where other forms of life cannot survive. The number of such dead zones increased from 149 in 2003 to over 200 in 2006. The continuing release pollutants from urban and agricultural sources combined with projected growth in coastal development and agricultural intensification may lead to a multiplication of the number of dead zones in the coming decades, unless substantial changes in policy are implemented.
When most people think of the dangers besetting the natural world, they think of the threat to other creatures. Declines in the numbers of such charismatic animals as pandas, tigers, elephants, whales, and various species of birds, have drawn world attention to the problem of species at risk. Species have been disappearing at up to 1000 times the natural rate, and this is predicted to rise dramatically. Based on current trends, an estimated 34,000 plant and 5,200 animal species - including one in eight of the world's bird species - face extinction. For thousands of years we have been developing a vast array of domesticated plants and animals important for food. But this treasure house is shrinking as modern commercial agriculture focuses on relatively few crop varieties. And, about 30% of breeds of the main farm animal species are currently at high risk of extinction.
While the loss of individual species catches our attention, it is the fragmentation, degradation, and outright loss of forests, wetlands, coral reefs, and other ecosystems that poses the gravest threat to biological diversity. Forests are home to much of the known terrestrial biodiversity, but about 45 per cent of the Earth's original forests are gone, cleared mostly during the past century. Despite some regrowth, the world's total forests are still shrinking rapidly, particularly in the tropics. Up to 10 per cent of coral reefs - among the richest ecosystems - have been destroyed, and one third of the remainder face collapse over the next 10 to 20 years. Coastal mangroves, a vital nursery habitat for countless species, are also vulnerable, with half already gone.
Global atmospheric changes, such as ozone depletion and climate change, only add to the stress. A thinner ozone layer lets more ultraviolet-B radiation reach the Earth's surface where it damages living tissue. Global warming is already changing habitats and the distribution of species. Scientists warn that even a one-degree increase in the average global temperature, if it comes rapidly, will push many species over the brink. Our food production systems could also be seriously disrupted.
The loss of biodiversity often reduces the productivity of ecosystems, thereby shrinking nature's basket of goods and services, from which we constantly draw. It destabilizes ecosystems, and weakens their ability to deal with natural disasters such as floods, droughts, and hurricanes, and with human-caused stresses, such as pollution and climate change. Already, we are spending huge sums in response to flood and storm damage exacerbated by deforestation; such damage is expected to increase due to global warming.
The reduction in biodiversity also hurts us in other ways. Our cultural identity is deeply rooted in our biological environment. Plants and animals are symbols of our world, preserved in flags, sculptures, and other images that define us and our societies. We draw inspiration just from looking at nature's beauty and power.
While loss of species has always occurred as a natural phenomenon, the pace of extinction has accelerated dramatically as a result of human activity. Ecosystems are being fragmented or eliminated, and innumerable species are in decline or already extinct. We are creating the greatest extinction crisis since the natural disaster that wiped out the dinosaurs 65 million years ago. These extinctions are irreversible and, given our dependence on food crops, medicines and other biological resources, pose a threat to our own well-being. It is reckless if not downright dangerous to keep chipping away at our life support system. It is unethical to drive other forms of life to extinction, and thereby deprive present and future generations of options for their survival and development.
Can we save the world's ecosystems, and with them the species we value and the other millions of species, some of which may produce the foods and medicines of tomorrow? The answer will lie in our ability to bring our demands into line with nature's ability to produce what we need and to safely absorb what we throw away.
