What distinguishes our home planet from the billions and billions of other celestial bodies in the infinitely vast universe is life. Life, as per our current knowledge, exists only on Earth. Only Earth has a biosphere that permeates the other spheres of air, land, and water.
Other planets may have atmospheres, similar terrestrial and chemi-cal compositions, or may even hold immense quantities of water as frozen ice. But those vast expanses are desolately barren. Only Earth is teeming with abundant life.
The origin of life on our home planet nearly 3.8 billion years ago and its magnificent evolution—nearly three-quarters of it in the pri-mordial oceans, before arriving on land—has been a stupendous saga.
As we have seen in our opening chapter, it was not that life happened to evolve on Earth; rather, it was life that molded our planet into the wonderful home for the millions of living beings that came into existence over millions of years. Life created its own womb where multifarious forms could exist and flourish, as an interconnected and interdependent web. All living beings on Earth, including human beings, can exist only as part of and as dependent on this common fabric of life. While the most unique feature of Earth is the existence of life, the most extraordinary feature of life itself is its magnificent diversity.1 Biological diversity (commonly referred to as biodiversity) refers precisely to the rich abundance of life, from genes through spe-cies and to ecosystems.2 The role of biological diversity in making our
1 Bradley J. Cardinale et al., “Biodiversity Loss and Its Impact on Humanity,”
nature 486 (2012): 59.
2 As Harvard biologist Edward O. Wilson has pointed out, as many as 10 bil-lion bacteria, belonging to as many as 6,000 species, live in only one gram of fertile soil. Edward O. Wilson, the creation: An Appeal to Save life on earth (New York: W. W. Norton, 2006), 18, 118.
home planet into a home or womb of life is not only invaluable but also indispensable.
It now appears that this web of life is coming under serious stress from the actions of its dominant species, namely, humanity. There is consensus in the scientific community today that the earth is on the verge of a sixth mass extinction of species and consequent loss of biodiversity. Biodiversity loss is yet another important facet of the contemporary ecological crisis—the global crisis that humanity is causing to the earth. The problem of species extinction is often underrated; it is overshadowed by the mounting concern for global warming and associated climate change. But the loss of biodiversity is a no less urgent threat to life on Earth.3 The exclusive attention to climate change can lead to the obfuscation of the multidimensional ecological crisis, of which climate change is certainly a part but not all of the problem.4 The problem of biodiversity loss is so huge and its consequences so far-reaching that it deserves much more attention than what is presently accorded to it.
In this chapter we first reflect on the importance of biological di-versity for the functioning of the biosphere in general and for human well-being in particular. Second, we review the current situation of biodiversity on Earth, taking stock of how our home planet is pre-cariously poised on the verge of a sixth mass extinction of species.
We will see evidence of the conspicuously anthropogenic character of this phenomenon. Third, we will examine the main drivers behind the current spasm of mass extinction of species: habitat loss and degrada-tion, climate change, overexploitadegrada-tion, polludegrada-tion, and invasion of alien species. Finally, we dwell on the consequences of the loss of biodiver-sity, moving from immediate consequences for human physical and economic well-being to ethical, aesthetic, and religious considerations.
Biodiversity and its importance
Virtually every part of our home planet—the continents, the oceans, and the atmosphere—teems with life, which is infinitely diverse and of which humanity forms an essential part.
3 Bo Normander, “Biodiversity: Combating the Sixth Mass Extinction,” in State of the World 2012: Moving towards Sustainable Prosperity (Washington, DC:
Worldwatch Institute, 2012), 169.
4 See also Michael J. Novacek, “Engaging the Public in Biodiversity Issues,”
Proceedings of the national Academy of Sciences 105 (2008): 11571, 11577; T. E.
Lovejoy and L. Hannah, eds., climate change and Biodiversity (New Haven, CT:
Yale University Press, 2005), 387–95.
“Biodiversity” is that rich spectrum of life—all of the world’s species ranging from the smallest bacteria to the giant redwoods;
from the algae in the sea to the wild dogs of the African savan-nahs; from the worms in the soil to the falcons soaring overhead.
Biodiversity embraces all the bacteria and other microbes, many of which perform vital chemical functions to keep ecosystems functioning. Biodiversity also includes the green plants that produce oxygen through photosynthesis, trapping solar energy and storing it in the form of sugars that are the base of energy resources for all other forms of life.
Biodiversity includes the fungi—mushrooms and their kin, responsible for decay, nutrient cycling, and chemical building blocks so vital to keep life going. And biodiversity also encom-passes the animals—everything from sponges to birds and mam-mals, including our own species, homo sapiens.5
Scientists use the term biodiversity to refer to all life—plants, ani-mals, and micro-organisms—and interactions among living organisms.
The term was used by the Harvard-based scientist Edward O. Wil-son6—the doyen of living biologists—in the 1988 proceedings from a conference held in 1986 organized by W. J. Rosen, who coined the term.7 The Millennium Ecosystem Assessment defines biodiversity as
“the variability among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within spe-cies, between spespe-cies, and of ecosystems.”8 As the global environment outlook 4 of 2007 succinctly states, “Biodiversity is the variety of life on Earth.”9
It is a paradox that in spite of all advances in human knowledge, we do not yet have a precise idea of the size of the family of life on Earth, of which we are an integral part. Even after decades of
5 Niles Eldredge, life in the Balance: humanity and the Biodiversity crisis (Princeton, NJ: Princeton University Press, 1998), vii.
6 See Edward O. Wilson, ed., Biodiversity (Washington, DC: National Academy Press, 1988).
7 See Novacek, “Engaging the Public in Biodiversity Issues,” 11571.
8 Millennium Ecosystem Assessment, ecosystems and human Well-being:
Biodiversity Synthesis (Washington, DC: World Resources Institute, 2005), 18.
The Millennium Ecosystem Assessment was a monumental work carried out between 2001 and 2005, involving 1,360 scientists from ninety-five countries. It encompassed both a global assessment and thirty-three sub-global assessments.
9 United Nations Environment Programme, the global environment outlook 4: environment for development (Nairobi: UNEP, 2007), 160.
painstaking work, only a fraction of the total species on Earth have been formally identified, between 1.7 and 2 million species. Probably fewer than 10 percent of living species have been identified and clas-sified. Estimates of the total number of species on Earth range from 5 million to 30 million (and conceivably even 100 million).10 The great tragedy is that a sizable portion of these are likely to be destroyed by humans before they have even been identified.
Biodiversity is crucial to the functioning of the biosphere. The bio-sphere, the realm of life that is the extraordinary, singularly unique feature of Earth, functions through a delicate equilibrium of an infinity of interactions among millions of living species.
This layer of living organisms—the biosphere—through the col-lective metabolic activities of its innumerable plants, animals, and microbes physically and chemically unites the atmosphere, geosphere, and hydrosphere into one environmental system within which millions of species, including humans, have thrived.
Breathable air, potable water, fertile soils, productive lands, bountiful seas, the equitable climate of Earth’s history, and other ecosystem services are manifestations of the workings of life.11 Biodiversity plays a critical role in underpinning ecosystem services that are vital to the functioning of the biosphere. Biodiversity ensures the regulation of climate, biogeochemical cycles, and hydrological functions. The carbon cycle and the water cycle, arguably the two most important large-scale processes for life on Earth, both depend on biodiversity at genetic, species, and ecosystem levels.12 Without the recycling of carbon and many other elements, life would quickly come to an end. While biodiversity is by no means the only driver of ecosystem functioning, which is also influenced by other abiotic fac-tors, it plays a significant role in assisting the ecosystems to maintain
10 Millennium Ecosystem Assessment, ecosystems and human Well-being:
Biodiversity Synthesis, 19; Paul R. Ehrlich and Edward O. Wilson, “Biodiversity Studies: Science and Policy,” Science 16 (1991): 758–62; Robert M. May, “How Many Species Are There on Earth?” Science 241 (1988): 1441–49; Richard Mackay, the Atlas of endangered Species (London: Earthscan, 2005), 7, 15;
“Biodiversity on the Brink” (editorial), nature climate change 1 (2011): 275.
11 Millennium Ecosystem Assessment, ecosystems and human Well-being:
Biodiversity Synthesis, 18.
12 Convention on Biological Diversity, “Biodiversity, Gender, and Climate Change” (Copenhagen, 2010), 1. Available online.
multiple functions, such as carbon storage,13 nitrogen and nutrient cycling, waste decomposition, seed dispersal, soil fertility, and so on.
Biodiversity provides the biospheric medium for energy and mate-rial flows, which in turn provide ecosystems with their functional properties.14 The more diverse an ecosystem is, the more ecological functions it performs. The loss of biodiversity can impair how natural ecosystems function by reducing the quantity and quality of services they provide.15
Biodiversity is critical to the equilibrium of the entire biosphere.
It is even more vital to human well-being, because it is the founda-tion of ecosystems that play a central role in supporting vital Earth systems upon which humanity depends. These services are often un-recognized or grossly undervalued. “The bacteria and microbes that transform waste into usable products, insects that pollinate crops and flowers, coral reefs and mangroves that protect coastlines, and the biologically-rich landscapes and seascapes that provide enjoyment are only a few” of these services.16 Biodiversity underpins a wide range of ecosystem services on which human societies have always depended for survival—from food and fresh water to medicine and protection from natural disasters—and to fulfill their cultural and spiritual needs.
Ecosystem services that are critical in supporting human well-being can be divided broadly into four categories:
1. Provisioning services, namely, the supply of goods directly consumed by people. This includes food from agricultural and forest ecosystems, fish from the oceans, rivers and lakes, medicines (from plants, animals and seaweeds) and cosmetic products, wood, fiber (including textiles), fuel, etc. Our supply and quality of fresh water also depends on ecosystems which play a critical role in circulating, cleaning, and replenishing water supplies.
13 It is estimated that for the period 2000–2008, land ecosystems removed roughly one-third of the CO2 emitted by human activities. See The National Academy of Sciences, Advancing the Science of climate change (Washington, DC: The National Academies Press, 2010), 56.
14 Norman Myers, “Environmental Services of Biodiversity,” Proceedings of the national Academy of Sciences 93 (1996): 2765.
15 See Fernando T. Maestre, “Plant Species Richness and Ecosystem Multifunc-tionality in Global Drylands,” Science 335 (2012): 214–15.
16 United Nations Environment Programme, global environment outlook 4, 158.
2. regulating services, which include a range of vital functions carried out by ecosystems. They include regulation of climate through the storing of carbon and control of local rainfall, the removal of pollutants by filtering the air and water, disease and pest regulation, protection from disasters such as landslides, avalanches, and especially from coastal storms through man-groves, coral reefs, kelp forests, etc.
3. Supporting services, which are essential to the functioning of ecosystems and therefore indirectly responsible for all other services. Examples are photosynthesis—a process fundamental to life on Earth, soil formation, nutrient cycling, etc. In fact, without ecosystems there would be no soil to support plants, and agriculture would be impossible. Another example is algae in ocean ecosystems which produce much of the oxygen that we breathe.
4. cultural and spiritual services, which respond to deeper needs and aspirations of people. They include the spiritual value attached to particular ecosystems such as sacred groves, and the aesthetic beauty of landscapes which have non-measurable value for art, recreation and tourism.17
The contributions of biodiversity in terms of ecosystem services to human well-being are invaluable. Biodiversity benefits people through more than just its contribution to material welfare and livelihoods;
it also contributes to security, resiliency, social relations, health, and freedom of choices and actions. As the basis for all ecosystem services, critical to the functioning of the entire biosphere and upon which human beings are entirely dependent, biodiversity plays a fundamen-tal role in maintaining and enhancing the well-being of the world’s more than 7 billion people, rich and poor, rural and urban alike.18 Biodiversity and human well-being are thus inextricably linked. The General Assembly of the United Nations, probably spurred by this awareness, declared the period 2011–20 the United Nations Decade on Biodiversity.
It appears that biodiversity, so crucial to the functioning of the biosphere and to human well-being, is now increasingly under threat
17 See Secretariat of the Convention on Biological Diversity, global Biodiversity outlook 3 (2010), 23; The National Research Council, ecological impacts of climate change (Washington, DC: The National Academies Press, 2008), 2.
18 See United Nations Environment Programme, global environment outlook 4, 160.
as our home planet is moving toward a sixth great mass extinction of species.
earth on the Brink of a massive Loss of Biodiversity Many scientists think that Earth is heading for a period of loss of biodiversity at an unprecedented scale. The decline in global biodiver-sity continues unabated, despite concerted efforts towards prevention and conservation. According to the Fourth Assessment Report of the IPCC in 2007, up to 30 percent of plant and animal species so far assessed are likely to be at increased risk of extinction if increases in global average temperatures exceed 1.5–2.5°C.19 If the temperatures rise further under the business-as-usual scenario, the loss of biodiver-sity will be even greater. At the same time, climate change is only one of the contributing factors to species extinction, and the synergistic effect of various human activities on Earth’s biodiversity can be even more devastating. Rigorous analyses of current and future scenarios consistently indicate that biodiversity will continue to decline over the twenty-first century and well into the future.20
Extinction is not a novelty in the evolutionary history of life on our home planet. In the past the biosphere has been exposed to climate variability and extremes and other natural events that have put pres-sure on Earth’s biodiversity. Fossil evidence abounds with testimonies of how the long march of the evolution of life has suffered innumer-able setbacks in terms of mass extinctions of species and consequent loss of biodiversity. Among these, five are canonically referred to as the great mass extinctions because of the wholesale severe biotic changes that occurred during each. These extinctions are listed below in chronological order:
1. the mass extinction at the end of the Ordovician era (nearly 439 million years ago), during which approximately 25 percent of the families and nearly 60 percent of the genera of marine organism were lost;
19 A. Fischlin et al., “Ecosystems: Their Properties, Goods, and Services,” in climate change: impacts, Adaptation and Vulnerability: contribution of Work-ing group ii to the fourth Assessment report of the intergovernmental Panel on climate change, ed. M. L. Parry et al. (Cambridge: Cambridge University Press, 2007), 213.
20 See Henrique M. Pereira et al., “Scenarios for Global Biodiversity in the Twenty-First Century,” Science 330 (2010): 1496–1501.
2. the late Devonian extinction (nearly 364 Mys), when 22 per-cent of marine families and 57 per22 per-cent of marine genera dis-appeared;
3. the Permian-Triassic extinction (nearly 251 Mys), the worst of the five mass extinctions, during which 95 percent of all species (marine as well as terrestrial) were lost;
4. the End Triassic extinction (nearly 199–214 Mys) during which marine organisms were most strongly affected (22 percent of marine families and 53 percent of marine genera were lost);
5. and the most recent mass extinction at the Cretaceous-Tertiary boundary (nearly 65 Mys) during which went extinct, among other species, the nonavian dinosaurs.21
Scientists now believe that a sixth mass extinction is imminent and predict that coming decades will see the loss of large numbers of spe-cies.22 There are already multiple indications of continuing decline in biodiversity in all three of its main components—genes, species, and ecosystems.23 We shall briefly discuss this three-tier loss of biodiversity at the genetic, species, and ecosystem levels.
Genetic diversity is in decline in natural ecosystems and in crop and livestock production. The decline in the population of species, combined with the fragmentation of landscapes, inland water bod-ies, and marine habitats, has necessarily led to an overall significant
21 For a detailed account of the five mass extinctions, see D. Jablonski, “Extinc-tions in the Fossil Record,” in extinction rates, ed. J. H. Lawton and R. M. May (Oxford: Oxford University Press, 1995), 25–44. For a synthetic summary of the five mass extinctions, see David B. Wake and Vance T. Vredenburg, “Are We in the Midst of the Sixth Mass Extinction? A View from the World of Amphibians,”
Proceedings of the national Academy of Sciences 105 (2008): 11466. See also D. H. Erwin, “Lessons from the Past: Biotic Recoveries from Mass Extinctions,”
Proceedings of the national Academy of Sciences 98 (2001): 1399–1403.
22 See Chris D. Thomas et al., “Extinction Risk from Climate Change,” nature 427 (2004): 145–48; J. A. Pounds et al., “Widespread Amphibian Extinctions from Epidemic Disease Driven by Global Warming,” nature 439 (2006): 161–67;
John C. Avise and Stephen P. Hubbell and Francisco J. Ayala, “In the Light of Evolution II: Biodiversity and Extinction,” Proceedings of the national Academy of Sciences 105 (2008): 11453; Wake and Vredenburg, “Are We in the Midst of the Sixth Mass Extinction?” 11466–73; Ilya M. D. Maclean and Robert J. Wilson,
“Recent Ecological Responses to Climate Change Support Predictions of High Extinction Risk,” Proceedings of the national Academy of Sciences 108 (2011):
12337.
23 See Secretariat of the Convention on Biological Diversity, global Biodiversity outlook 3, 9.
decline in the genetic diversity of life on Earth.24 It is feared that we may have already eradicated three-quarters of the planet’s agricultural crop genetic diversity.25 Of particular concern is the general trend to-ward homogenization that is such a strong characteristic of modern agriculture.
While this [genetic] decline is of concern for many reasons, there is particular anxiety about the loss of diversity in the varieties and breeds of plants and animals used to sustain human liveli-hoods. A general homogenization of landscapes and agricultural varieties can make rural populations vulnerable to future changes if genetic traits kept over thousands of years are allowed to disappear.26
Examples of the drastic reduction of genetic biodiversity are found all over the world. It is estimated that crop diversity has been greatly reduced in China, with the number of local rice varieties being culti-vated having witnessed a decline from 46,000 in the 1950s to slightly more than 1,000 in 2006. Loss of genetic diversity is evident also in the case of livestock breeds. Approximately 21 percent of the world’s 7,000 livestock breeds are classified as being at risk, and a further 36 percent are of unknown risk status. More than sixty breeds are reported to have become extinct in the first decade of this century
Examples of the drastic reduction of genetic biodiversity are found all over the world. It is estimated that crop diversity has been greatly reduced in China, with the number of local rice varieties being culti-vated having witnessed a decline from 46,000 in the 1950s to slightly more than 1,000 in 2006. Loss of genetic diversity is evident also in the case of livestock breeds. Approximately 21 percent of the world’s 7,000 livestock breeds are classified as being at risk, and a further 36 percent are of unknown risk status. More than sixty breeds are reported to have become extinct in the first decade of this century