Coral reefs, the “rainforests of the sea”
The term biodiversity, first used in 1985, is a contraction of “biological diversity” and is a measure of variation among living organisms from all sources. It includes terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are part. Biodiversity is organized at three levels: ecosystems, species comprising the ecosystems, and genes prescribing the traits of the species. Changes in global biodiversity are the product of two opposing processes: (i) the success of organisms in spreading in local, regional and, ultimately, global ecosystems and (ii) changes in the environment that prevent organisms from existing or spreading. There have been periods of rapid expansion, relative stability and rapid decline. In fact, five of the periods of decline were so dramatic that they are recognised as mass extinction events
How important is biological diversity for the functioning of the planet? Do species really matter? If so, which ones and why? How much diversity or complexity in ecological systems can be lost before critical Earth System functions are impaired? Bodiversity plays significant roles in buffering shocks and extreme events, and in regime shift dynamics. Biodiversity as a whole forms a shield protecting each of the species that together compose it, ourselves included, and as E.O. Wilson reminds us, during the Anthropocene, Earth’s shield of biodiversity is being shattered and the pieces are being thrown away.
Biodiversity and a resilient biosphere are a reflection of life continuously being confronted with uncertainty and the unknown. Diversity builds and sustains insurance and keeps systems resilient to changing circumstances. we ourselves are possibly among the endangered species. Our turn for extinction will also come, but we should avoid speeding its arrival. Our own existence is not independent of that of biodiversity: we rely on a wide range of services that other species provide, and their demise hastens our own. As E.O. Wilson warns us, “Unless humanity learns a great deal more about global biodiversity and moves quickly to protect it, we will soon lose most of the species composing life on Earth. Humanity is losing the race between the scientific study of global biodiversity and the obliteration of countless still-unknown species.”
Natural systems help secure the very conditions that permit our survival, moderating weather, stabilizing soil, coastlines, and climate; influencing our atmosphere; and in general making it possible for humans to exist and persist. They do not maintain those conditions in order to preserve the world for Homo sapiens ; rather, Homo sapiens exists because those conditions permit it to do so. The subtlety of this distinction should not disguise the importance of the lesson. That is, we cannot count on the biosphere to maintain the biota and environment to our specifications; the world is constantly in transition, more so today than ever before in recorded history. Biodiversity is being lost at alarming rates, and with it the services that sustain the human population. Should we care? We had better care if we care about our own survival.
For E.O. Wilson, The diversity of life forms, so numerous that we have yet to identify most of them, is “the greatest wonder of this planet.” We have never fathomed its limits, and we do not know the true number of species on Earth, even to the nearest order of magnitude. According to Wilson, “biodiversity is our most valuable but least appreciated resource […] It is a potential source for immense untapped material wealth, in the form of food, medicines, and amenities. Wilson has also suggested that humans possess an innate tendency to seek connections with nature and other forms of life. He introduced and popularized this hypothesis in his book, Biophilia (1984). Wilson defines biophilia as "the urge to affiliate with other forms of life".
Biodiversity is essential for ability of ecosystems to provide services necessary for human well-being and for other forms of life. They enrich the soil and create the very air we breathe. The genetic diversity contained in the range of species and populations underpins their fitness and adaptive potential. Biodiversity is not distributed evenly on Earth, and is richer in the tropics. It follows a latitudinal gradient, with the largest number of species occurring in the equatorial regions of South America, Africa, and Asia. Some factors that contribute to biodiversity include a fairly stable climate, productivity, and the size of the organisms (smaller mobile organisms can much more easily diversify than larger ones) as well as the size of their foraging areas, measured as fractals related to their size. As Wilson puts it, Mother Earth, lately called Gaia, is no more than the commonality of organisms and the physical environment they maintain with each passing moment, an environment that will destabilize and turn lethal if the organisms are disturbed too much.
Rain forests and coral reefs are some of the most diverse habitats on the planet. Tropical rain forests occupy only 6 percent of the earth’s land surface, but are believed to contain more than half of the species of organisms on earth. More than 25 percent of all marine species are found on coral reefs, which occupy less than one percent of the ocean. Every organism in an eccosystem plays a unique role and contributes to how specific communities survive and function. High biodiversity ensures the health these environments.
An “awful symmetry” characterizes the relative measures of biodiversity and industrial development worldwide. While the rich industrialized nations of the “Global North” occupy the smallest and least interesting biota, the poorer nations of the “Global South” — those with the fastest-growing populations — live next to the richest deposits of biological diversity. (The Diversity of Life, p.260) These differences account for many of the issues facing calls for addressing sustainable development in the face of global warming.
Human actions are fundamentally, and to a significant extent irreversibly, changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity. Livestock and humans now account for nearly 96% of all mammal biomass on Earth, and more species are threatened with extinction than ever before in human history. Climate change increasingly interacts with these processes. Over the past few hundred years, humans have increased species extinction rates by as much as 1,000 times the background rates that were typical over Earth's history, and the distribution of species on Earth is becoming more homogeneous. Changes in important components of biological diversity were more rapid in the past 50 years than at any time in human history. Projections and scenarios indicate that these rates will continue, or accelerate, in the future. --Milenium Ecosystem Assessment, 2005.
The loss of biological diversity is an aspect of global change that may prove to be just as important as climate change. The human perception that significant disruption of Earth’s complex webs of life is an inherently dangerous path may be more effective than scientific knowledge of the impacts of diversity change on ecosystem functioning. Changes in global biodiversity are the product of two opposing processes: the success of organisms in spreading in local, regional and, ultimately, global ecosystems, versus changes in the environment that prevent organisms from existing or spreading.
fungi of Saskatchewan
The main human threats to biodiversity are habitat loss or fragmentation and increased access to remote regions. Conservation biology seeks to quantify the relations between habitat and populations and to guide efforts to limit extinctions.
The theory of island biogeography correlates the balance of immigration and extinction over time for a given bounded area. A rule of thumb is that a ten-fold increase in area results in a doubling of species, and that when a habitat has lost 90% of its extent, it will eventually lose half its species.
“Human hunters help no species” As the Mexican truck driver said, after shooting one of the last two imperial woodpeckers, largest of all the world’s woodpeckers, “It was a great piece of meat.” ( The Diversity of Life, p.241)
The bushmeat trade has threatened many species whose extinction would irrevocably upset the balance of many ecosystems. These include predators that keep rodents in check, species vital for dispersing seeds and others such as bats that pollinate flowers.
Bush Meat on Sale in Equatorial Gunea
The number of hunters involved has gone up, and the penetration of road networks into the remotest places is such that there is no refuge left. So it becomes commercially possible to make a trade out of something that was once just a rabbit for the pot.
The problem of exotics also poses threats to biodiversity. Invasive species are the second most common threat associated with extinction, behind hunting, fishing or harvesting, particularly in island environments, where endemic species have small populations and are poorly adapted for predators or environmental changes. Cats, rats and goats are among the most common offenders, along with microorganisms like the amphibian-killing chytrid fungus and the avian malaria parasite
For the Indian activist Vandana Shiva, biodiversity has always been a local, commonly shared resource on which indigenous communities have been dependent for their livelihood. The current moves in many countries of the South to introduce new intellectual property laws under the GATT/WTO agreements to, in effect, 'enclose' these 'commons' and bring them under a regime of private property and patents for the benefit of corporations, are a grave threat to their very survival.