“Honing Homo sapiens: From Pests to Catalysts” by Gleo Agustein G. Sevilla
The existence and diversity of life are the main features of mankind’s home, the Earth. Approximately nine million types of plants, animals, protists and fungi inhabit the Earth. These are in addition to the seven billion people of today (Cardinale et al., 2012). Biodiversity can truly be considered as the core of humanity’s existence.
Biodiversity is a contraction of “biological diversity.” It refers to the number, variety and variability of living organisms. Although many definitions of biodiversity exist, the definition provided by the Convention on Biological Diversity is the most cited. According to it, “biological diversity means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems” (Hens and Boon, 2003).
Numerous threats to biodiversity exist today, however. According to Schulze and Mooney (1994), the five main threats to biodiversity are habitat loss, climate change, overexploitation, invasive alien species and pollution. First, habitat loss is the result of the transformation or modification of natural environments in order to fulfill human needs. Common types of habitat loss include cutting down forests for timber and making dams out of rivers to have more water available for agriculture and cities. Second, climate change is caused by a build-up of greenhouse gases such as carbon dioxide in the Earth’s atmosphere. Climate change alters the climate patterns and ecosystems in which species have evolved and on which they depend. Third, overexploitation, or unsustainable use, happens when biodiversity is removed faster than it can be replenished and, over the long term, can result in the extinction of species. For example, Encephalartos brevifoliolatus, a cycad, is now extinct in the wild after being overharvested for horticulture utilization. Fourth, invasive alien species are species that have spread outside of their natural habitat and threaten biodiversity in their new area. These species are harmful to native biodiversity in a number of ways, for example as predators, parasites, vectors of disease or direct competitors for habitat and food. Fifth, pollution is a growing threat on both land and in aquatic ecosystems. While the large-scale use of fertilizers has allowed for the increased production of food, it has also caused severe environmental damage (Schulze and Mooney, 1994). All these drivers of biodiversity loss have human activities as contributors, as shown in Figure 1 (Chapin et al., 2000).
Figure 1. The role of biodiversity in global changes (Chapin et al., 2000).
At the first Earth Summit, which was approximately two decades ago, most nations or countries declared that human actions and activities were dismantling the Earth’s ecosystems, and eliminating genes, species and biological traits at a very alarming rate (Cardinale et al., 2012).
Humans have detrimental contributions on biodiversity loss. This can be traced back to humanity’s own history. For instance, in the Americas, charismatic large-bodied animals such as saber-toothed cats (Smilodon spp.), mammoths (Mammuthus spp.), and giant ground sloths (Megalonyx jeffersonii) vanished after humans arrived around 11,000 to 13,000 years ago. Similar losses occurred in Australia 45,000 years ago and in many oceanic islands within a few hundred years of the arrival of humans. Classic examples of the loss of island endemics include the dodo (Raphus cucullatus) from Mauritius, moas (e.g., Dinornis maximus) from New Zealand, and elephant birds (Aepyornis maximus) from Madagascar (Sodhi et al., n.d.).
Humans have continuously damaged the biodiversity up to the present time. The rate and extent of extinctions caused by humans have been debated. However, there is a general agreement that extinction rates have increased in the recent hundred years due to the abrupt habitat destruction from European colonialism and from continuous expansion of human population (Sodhi et al., n.d.). Alteration in the global environment, changes in global biogeochemical cycles, transformations of lands and enhancement of the mobility of biota have occurred due to humankind. Fossil-fuel combustion and deforestation have increased the concentration of atmospheric carbon dioxide (CO2) by 30% in the past three centuries. Human activities have more than doubled the concentration of methane and increased concentrations of other gases that contribute to global warming. In the next century, these greenhouse gases are likely to cause the most rapid climate change that the Earth has experienced since the end of the last glaciation 18,000 years ago and perhaps a much longer time. Industrial fixation of nitrogen for fertilizer and other human activities have more than doubled the rates of terrestrial fixation of gaseous nitrogen into biologically available forms. The run off of nutrients from agricultural and urban systems has increased also in the developed river basins of the Earth, resulting to major ecological changes in estuaries and coastal zones. Humans have transformed 40% to 50% of the ice-free land surface. Humans have changed prairies, forests and wetlands into agricultural and urban system. Humans dominate about one-third of the net primary productivity on land and harvest fish that use 8% of ocean productivity. In fact, 54% of the available fresh water is being utilized. This use is even projected to increase to 70% by 2050. Finally, the mobility of people has transported organisms across geographical barriers that have kept the biotic regions of the Earth separated. As a result, many of the ecologically important plant and animal species of many areas have been introduced in foreign areas (Chapin et al., 2000).
The extinction of certain species such as large predators and pollinators may have more devastating ecological consequences than the extinction of others. Ironically, avian vulnerability to predation is often worsen when certain large predatory species become rarer in tropical communities. For example, although large cats such as jaguars (Panthera onca) do not prey on small birds directly, they exert a limiting force on smaller predators such as medium-sized and small mammals, which become more abundant with the former species’ decline. Conservation biologists have traditionally focused on the study of the independent declines or extinctions of individual species while paying relatively less attention to the possible effects of species coextinctions (e.g., hosts and their parasites). However, it is likely that many coextinctions between interdependent taxa have occurred, but most have gone unnoticed in these relatively understudied systems. For example, an extinct feather louse (Columbicola extinctus) was discovered in 1937, 23 years after likely coextinction with its host passenger pigeon (Ectopistes migratorius) (Sodhi et al., n.d.).
Biodiversity provides or modifies the resources that we use to satisfy our basic needs such as drinking water, food, shelter and medicines. Thus, biodiversity is essential to our health (Ostfeld and Keesing, 2013). Biodiversity loss can threaten countless human lives. While many people have benefited over the last century from the conversion of natural ecosystems to human-dominated ecosystems, other people have constantly suffered from the consequences (Green Facts, n.d.). The world’s poor will most likely bear the immediate and direct costs of biodiversity losses. Nevertheless, it is clear from these and many other international studies that the world as a whole will be affected (Slingenberg et al., n.d.).
Figure 2. Worldwide depiction of threatened biodiversity hotspots (Slingenberg et al., n.d.).
The loss of biodiversity is expected to continue at an unchanged increasing pace in the coming decades. Key underlying drivers, global population and economic activity are expected to keep on growing. Between 2000 and 2050, the global population is projected to grow by 50% and the global economy will quadruple. The need for food, energy and wood will unavoidably lead to a decrease in and unsustainable use of natural resources. The negative impacts of climate change, nitrogen deposition, fragmentation, infrastructure and unchecked human settlement on biodiversity will further expand. As a result, global biodiversity is projected to decrease from about 70% in 2000 to about 63% by 2050. Figure 2 provides an overview of worldwide critically endangered, vulnerable and relatively stable or intact biodiversity hotspots (Slingenberg et al., n.d.).
Humans are the roots of biodiversity loss and are also the ones suffering from its detrimental fruits. Human effects on climate, biogeochemical cycles, land use and mobility of organisms have changed the local and global diversity of the planet, with important ecosystem and societal consequences. Hence, humans hold the solutions as well. Humans are the only ones who can save biodiversity, the very core of life’s existence. Humans are the only ones who can change from being the “pests” to being the “catalysts” for inclusive change and betterment.
