International Environment month is going now. From the beginning of the world, whatever has been the most impactful part of our world is its biodiversity. From then till today, its impact is so huge that no one can even feel its depth and complexity. So to utilize a little of that and our sins, it’s important for us to go through a analysis.
Biodiversity or Biological diversity is a term that describes the variety of living beings on earth. In short, it is described as a degree of variation of life. Biological diversity encompasses microorganisms, plants, animals, and ecosystems, such as coral reefs, forests, rainforests, deserts, etc.
And after going through and analysis, I’ve found us as the most shameless livings on the earth and it let me feel sorry, very very sorry for some days. In this series, I’ll try to touch there in your heart so that you can also feel sorry, be aware. There will be 4 parts of the document and I’ve also tried to create a map of our duties and responsibilities and so I hope every readers will be with us in each part. Carefully, understanding.
Reason for loss of biodiversity:
- Human activities and loss of habitat
- Marine environment
- Increasing Wildlife trade
- Climate change
- Invasive species
- Over-exploitation of natural resources
- Position in food chain
- Degree of specialization
- Over consumption
How they are becoming reasons for the loss of biodiversity?
Human activities and loss of habitat : Human activity is by far the biggest cause of habitat loss. The planet’s human population has doubled in the past 50 years and the pressure to house and feed more than seven billion people has seen incursions into previously pristine natural habitats increase dramatically. At the same time, human impacts on the Earth’s climate are radically changing weather patterns and, as a result, the spread and nature of wild habitats. The primary individual cause of loss of habitat is the clearing of land for agriculture. An estimated 177,000 square kilometres of forests and woodlands are cleared annually to make space for farming or in order to harvest timber for fuel and wood products. Estimates suggest the Earth has lost about half of its forests in 8,000 years of human activity, with much of this occurring in recent decades. About 3% of forests have been lost since the 1990s alone. And its not just forest clearing that leads to habitat loss. The loss of wetlands, plains, lakes, and other natural environments all destroy or degrade habitat, as do other human activities such as introducing invasive species, polluting, trading in wildlife, and engaging in wars. This destruction of habitat also involves marine zones and the ocean, with urbanisation, industrialisation and tourism all aff ecting habitats in coastal areas. Some 40% of the global population live within 100 kilometres of the coast, placing major strains on wetlands and oceans.
Human activity is by far the biggest cause of habitat loss. The planet’s human population has doubled in the past 50 years and the pressure to house and feed more than seven billion people has seen incursions
into previously pristine natural habitats increase dramatically. At the same time, human impacts on the Earth’s climate are radically changing weather patterns and, as a result, the spread and nature
of wild habitats. The primary individual cause of loss of habitat is the clearing of land for agriculture. An estimated 177,000 square kilometres of forests and woodlands are cleared annually to make space for farming or in order to harvest timber for fuel and wood products. Estimates suggest the Earth has lost about half of its forests in 8,000 years of human activity, with much of this occurring in recent decades. About 3% of forests have been lost since the 1990s alone. And its not just forest clearing that leads to habitat loss. The loss of wetlands, plains, lakes, and other natural environments all destroy or degrade habitat, as do other human activities such as introducing invasive species, polluting, trading in wildlife, and engaging in wars. This destruction of habitat also involves marine zones and the ocean, with urbanization, industrialization and tourism all affecting habitats in coastal areas. Some 40% of the global population live within 100 kilometres of the coast, placing major strains on wetlands and oceans..
Deforestation: Conversion of forests for other land uses, including pulp, palm, and soy plantations, pastures, settlements, roads and infrastructure.
Each year, fires burn millions of hectares of forest worldwide. Fires are a part of nature but degraded forests are particularly vulnerable. These include heavily logged rainforests, forests on peat soils, or where forest fires have been suppressed for years allowing unnatural accumulation of vegetation that makes the fire burn more intensely. The resulting loss has wide-reaching consequences on biodiversity, climate, and the economy.
Illegal logging occurs in all types of forests across all continents – from Brazil to Indonesia – destroying nature and wildlife, taking away community livelihoods and distorting trade. Illegally harvested wood finds its way into major consumption markets, such as the U.S., and European Union, which further fuels the cycle.
Over-harvesting for domestic use or for commercial trade in charcoal significantly damages forests.
The impact of mining on tropical forests is growing due to rising demand and high mineral prices. Mining projects are often accompanied by major infrastructure construction, such as roads, railway lines and power stations, putting further pressure on forests and freshwater ecosystems.
The single biggest direct cause of tropical deforestation is conversion to cropland and pasture, mostly for subsistence, which is growing crops or raising livestock to meet daily needs. The conversion to agricultural land usually results from multiple direct factors. For example, countries build roads into remote areas to improve overland transportation of goods. The road development itself causes a limited amount of deforestation. But roads also provide entry to previously inaccessible—and often unclaimed—land. Logging, both legal and illegal, often follows road expansion (and in some cases is the reason for the road expansion). When loggers have harvested an area’s valuable timber, they move on. The roads and the logged areas become a magnet for settlers—farmers and ranchers who slash and burn the remaining forest for cropland or cattle pasture, completing the deforestation chain that began with road building. In other cases, forests that have been degraded by logging become fire-prone and are eventually deforested by repeated accidental fires from adjacent farms or pastures.
Although poverty is often cited as the underlying cause of tropical deforestation, analyses of multiple scientific studies indicate that that explanation is an oversimplification. Poverty does drive people to migrate to forest frontiers, where they engage in slash and burn forest clearing for subsistence. But rarely does one factor alone bear the sole responsibility for tropical deforestation.
State policies to encourage economic development, such as road and railway expansion projects, have caused significant, unintentional deforestation in the Amazon and Central America. Agricultural subsidies and tax breaks, as well as timber concessions, have encouraged forest clearing as well. Global economic factors such as a country’s foreign debt, expanding global markets for rainforest timber and pulpwood, or low domestic costs of land, labor, and fuel can encourage deforestation over more sustainable land use.
Access to technology may either enhance or diminish deforestation. The availability of technologies that allow “industrial-scale” agriculture can spur rapid forest clearing, while inefficient technology in the logging industry increases collateral damage in surrounding forests, making subsequent deforestation more likely. Underlying factors are rarely isolated; instead, multiple global and local factors exert synergistic influences on tropical deforestation in different geographic locations.
Cultivations and livestock farming
We should consider, in fact, that with regards to the substitution of forest areas with cultivations and livestock farms, the impact is much higher because after the extraction of the most precious trees which are destined for timber commercialization, forests are set on fire causing a great impact on local animals and plants. The most disastrous year for the Amazon forest has been 1991 when over 50,000 fires where registered by aerial views or satellite images.
Centuries-old trees are cut down to make timber or cellulose for the furniture or paper industry. Any system employed for wood cutting causes serious damage to the ecosystem, and these damages are amplified by construction of roads required for vehicles and to trasport chopped timber to its destination. For this reason, also many other economically unattractive trees which have an important biological and ecological value are are cut down.
This activity is undertaken especially by native populations, which due to recent population growth, must provide energy sources for their survival. This phenomenon adds to large-scale industrial timber exploitation.
Besides the construction of roads to transport timber, also dam construction and industrial exploitation of mines contribute to massive deforestation.
Desertification: Desertification is land degradation in arid, semi-arid, and dry sub-humid areas, collectively known as drylands, resulting from many factors, including human activities and climatic variations. In general, desertification is caused by variations in climate and by unsustainable land-management practices in dryland environments. By their very nature, arid and semiarid ecosystems are characterized by sparse or variable rainfall. Thus, climatic changes such as those that result in extended droughts can rapidly reduce the biological productivity of those ecosystems. Such changes may be temporary, lasting only a season, or they may persist over many years and decades. On the other hand, plants and animals are quick to take advantage of wetter periods, Since dryland environments are used for a variety of human purposes (such as agriculture, animal grazing, and fuel wood collection), the various activities undertaken in them can exacerbate the problem of desertification and bring about lasting changes to dry land ecosystems. In 1977, at the United Nations Conference on Desertification (UNCOD) in Nairobi, Kenya, representatives and delegates first contemplated the worldwide effects of desertification. The conference explored the causes and contributing factors and also possible local and regional solutions to the phenomenon. In addition, the delegates considered the varied consequences of desertification, such as crop failures or decreased yields in rain-fed farmland, the loss of perennial plant cover and thus loss of forage for livestock, reduced woody biomass and thus scarcity of fuelwood and building materials, a decrease in potable water stocks from reductions in surface water and groundwater flow, increased sand dune intrusion onto croplands and settlements, increased flooding due to rising sedimentation in rivers and lakes, and amplified air and water pollution from dust and sedimentation.
In many dryland areas, spread of invasive plants has led to losses in ecosystem services (high confidence), while over-extraction is leading to groundwater depletion (high confidence). Unsustainable land management, particularly when coupled with droughts, has contributed to higher dust-storm activity, reducing human well-being in drylands and beyond (high confidence).
Climate variability and anthropogenic climate change, particularly through increases in both land surface air temperature and evapotranspiration, and decreases in precipitation, are likely to have played a role, in interaction with human activities, in causing desertification in some dryland areas. The major human drivers of desertification interacting with climate change are expansion of croplands, unsustainable land management practices and increased pressure on land from population and income growth.
Invasive plants contributed to desertification and loss of ecosystem services in many dryland areas in the last century (high confidence) (Section 3.7.3).
Extensive woody plant encroachment altered runoff and soil erosion across much of the drylands, because the bare soil between shrubs is very susceptible to water erosion, mainly in high-intensity rainfall events (Manjoro et al. 2012; Pierson et al. 2013; Eldridge et al. 2015). Rising CO2 levels due to global warming favour more rapid expansion of some invasive plant species in some regions. An example is the Great Basin region in western North America where over 20% of ecosystems have been significantly altered by invasive plants, especially exotic annual grasses and invasive conifers, resulting in loss of biodiversity. This land-cover conversion has resulted in reductions in forage availability, wildlife habitat, and biodiversity (Pierson et al. 2011, 2013
; Miller et al. 2013).
In the arid Algerian High Plateaus, desertification due to both climatic and human causes led to the loss of indigenous plant biodiversity between 1975 and 2006 (Hirche et al. 2011). Ayoub (1998) identified 64 Mha in Sudan as degraded, with the Central North Kordofan state being most affected. Here we’re going to explain their effects according to clarifications of biodiversity:
Over 20% of global plant biodiversity centres are located within drylands (White and Nackoney 2003). Plant species located within these areas are characterised by high genetic diversity within populations (Martínez-Palacios et al. 1999). The plant species within these ecosystems are often highly threatened by climate change and desertification (Millennium Ecosystem Assessment 2005b; Maestre et al. 2012). Increasing aridity exacerbates the risk of extinction of some plant species, especially those that are already threatened due to small populations or restricted habitats (Gitay et al. 2002). Desertification, including through land-use change, already contributed to the loss of biodiversity across drylands (medium confidence) (Newbold et al. 2015; Wilting et al. 2017). For example, species richness decreased from 234 species in 1978 to 95 in 2011 following long periods of drought and human driven degradation on the steppe land of south-western Algeria (Observatoire du Sahara et du Sahel 2013). Similarly, drought and overgrazing led to loss of biodiversity in Pakistan to the point that only drought-adapted species can now survive on the arid rangelands (Akhter and Arshad 2006). Similar trends were observed in desert steppes of Mongolia (Khishigbayar et al. 2015). In contrast, the increase in annual moistening of southern European Russia from the late 1980s to the beginning of the 21st century caused the restoration of steppe vegetation, even under conditions of strong anthropogenic pressure (Ivanov et al. 2018). The seed banks of annual species can often survive over the long term, germinating in wet years, suggesting that these species could be resilient to some aspects of climate change (Vetter et al. 2005). Yet, Hiernaux and Houérou (2006) showed that overgrazing in the Sahel tended to decrease the seed bank of annuals, which could make them vulnerable to climate change over time. Perennial species, considered as the structuring element of the ecosystem, are usually less affected as they have deeper roots, xeromorphic properties and physiological mechanisms that increase drought tolerance (Le Houérou 1996). However, in North Africa, long-term monitoring (1978–2014) has shown that important plant perennial species have also disappeared due to drought (Stipa tenacissima and Artemisia herba alba) (Hirche et al. 2018; Observatoire du Sahara et du Sahel 2013). The aridisation of the climate in the south of Eastern Siberia led to the advance of the steppes to the north and to the corresponding migration of steppe mammal species between 1976 and 2016 (Ivanov et al. 2018).
Dryland ecosystems have high levels of faunal diversity and endemism (MEA 2005; Whitford 2002). Over 30% of the endemic bird areas are located within these regions, which is also home to 25% of vertebrate species (Maestre et al. 2012; MEA 2005). Yet, many species within drylands are threatened with extinction (Durant et al. 2014; Walther 2016). Habitat degradation and desertification are generally associated with biodiversity loss (Ceballos et al. 2010; Tang et al. 2018; Newbold et al. 2015). The ‘grazing value’ of land declines with both a reduction in vegetation cover and shrub encroachment, with the former being more detrimental to native vertebrates (Parsons et al. 2017). Conversely, shrub encroachment may buffer desertification by increasing resource and microclimate availability, resulting in an increase in vertebrate species abundance and richness observed in the shrub-encroached arid grasslands of North America (Whitford 1997) and Australia (Parsons et al. 2017). However, compared to historically resilient drylands, these encroached habitats and their new species assemblages may be more sensitive to droughts, which may become more prevalent with climate change (Schooley et al. 2018). Mammals and birds may be particularly sensitive to droughts because they rely on evaporative cooling to maintain their body temperatures within an optimal range (Hetem et al. 2016) and risk lethal dehydration in water limited environments (Albright et al. 2017). The direct effects of reduced rainfall and water availability are likely to be exacerbated by the indirect effects of desertification through a reduction in primary productivity. A reduction in the quality and quantity of resources available to herbivores due to desertification under changing climate can have knock-on consequences for predators and may ultimately disrupt trophic cascades (limited evidence, low agreement) (Rey et al. 2017; Walther 2010). Reduced resource availability may also compromise immune response to novel pathogens, with increased pathogen dispersal associated with dust storms (Zinabu et al. 2018). Responses to desertification are species-specific and mechanistic models are not yet able to accurately predict individual species’ responses to the many factors associated with desertification (Fuller et al. 2016).
Destruction of marine environment: Biotic impoverishment is an almost inevitable consequence of the ways in which the human species has used and misused the environment. The main root causes of biodiversity loss lie in: demographic pressure and unsustainable use of natural resources; economic policies that fail to value the environment and its resources; insufficient knowledge and its poor application; weakness in legal and institutional systems (Dugan 1990, McNeely et ai. 1990, UNEP 1984b, WRIIIUCN/UNEP 1992).
Human population growth and unsustainable use of resources: The global human population is quickly rising towards the 6 billion mark. Almost 70% of this population lives near aquatic systems, especially coastal zones. In countries with high fertility rates, about half of the populations is under 16.
The resulting demographic momentum in coming years, due to this large number of people reaching their reproductive age, means that the global population will continue to grow for at least the next half-century. The rates and magnitude of this growth depend on social and economic measures, especially on economic development in developing countries (WRIIIUCN/UNEP 1992). As numbers increase, the consumption ofrenewable and non-renewable resources has a higher rate of increase. The recreational use of coastal waters is also increasing, in some areas representing the major industry. Coastal tourism generally shows peaks in tourist numbers in certain areas, especially those with high biodiversity such as coral reefs, and at certain times of the year. High tourist numbers put additional pressure on coastal biodiversity through excessive food, energy and water consumption, physical alterations of the environment (infrastructural development, boating, trampling), and cultural alterations (Schoor! & Visser 1991). Ironically, this environmental degradation and congestion may destroy the main natural assets on which tourism development is based.
Economic systems and policies that fail to value the environment and its resources: Conversions of natural systems to farmlands or industrial areas take place due to the urgent need for economic land use. These developments are often economically and biologically unsound because they are implemented regardless of sustainability, and because natural habitats are commonly under- valued. There are several reasons for the mis-valuation of biological resources. Many resources, such as food, fuelwood and medicinal plants, are consumed directly and never enter markets. Many values of coastal biotopes do not have markets, such as water purification, storm surge protection, and nursery grounds for fisheries products. Because these are \’free goods\’ they tend to be ignored in economic calculations loss of that decide whether such biotopes should be conserved or developed (McNeely , et al. 1990). The result is a systematic bias favoring development and hence degradation of coastal ecosystems.
Economic policies in many African countries contribute to environmental degradation as the need for foreign exchange earnings often forces countries to increase environmental exploitation, such as for wood, minerals and marine which products. Another aspect is the inequity in ownership and flow of benefits from causes both the use and conservation of biological resources (McNeely et al. 1990). Too often the local communities, who are dependent on the natural resources, are left out of planning but in the end pay the price.
Deficiencies in knowledge and its application: Scientists still do not have adequate knowledge of coastal ecosystems and their innumerable components (Martens & Jaccarini 1990). Even where information exists it does not flow efficiently to decision-makers, who have often failed to develop policies that reflect the scientific, economic, social and ethical values of les. In coastal biodiversity (Dugan 1990, McNeely et al. 1990, WRIIIUCN/UNEP 5. The 1992).
Except for research on commercially important resources, until recently of most marine research had scientific rather than resource-management goals. Few n will databases on marine subjects exist that are accessible or informative enough for of policy-makers, especially on a regional and international scale. An additional difficulty in coordinating information collection and transfer relates to overlapping jurisdictions and competition among agencies concerned with marine resources. A final difficulty is often public reluctance to accept policies that reduce excessive resource consumption, which shows an urgent need for more public awareness in campaigns.
Weak legal and institutional systems: Most countries have different institutions that are responsible for managing coastal, resources, but each of them focuses on only one aspect such as agriculture, fisheries y. this or tourism. Ecological realities, however, clearly call for a cross-sectoral approach including local-community participation. It is only quite recently that multidisciplinary and institutional collaboration has been established to facilitate communication and information exchange among all concerned groups. Many developing countries lack adequate environmental laws and enforcement instruments to ensure protection of the environment and sustainable use resources to (Dugan 1990, McNeely et al. 1990). Largely because of these institutional and legal constraints, biodiversity conservation and management has typically been fragmented and restricted to specific protected areas or species. However, integrated and regional approaches are needed to address the habitat needs of whole such biotic communities in relation to development programs.
Humans and Mother Nature share blame in the destruction of ocean habitats, but not equally.
Hurricanes and typhoons, storm surges, tsunamis and the like can cause massive, though usually temporary, disruptions in the life cycles of ocean plants and animals. Human activities, however, are significantly more impactful and persistent.
Wetlands are dredged and filled in to accommodate urban, industrial, and agricultural development. Cities, factories, and farms create waste, pollution, and chemical effluent and runoff that can wreak havoc on reefs, sea grasses, birds, and fish.
Inland dams decrease natural nutrient-rich runoff, cut off fish migration routes, and curb freshwater flow, increasing the salinity of coastal waters. Deforestation far from shore creates erosion, sending silt into shallow waters that can block the sunlight coral reefs need to thrive.
Destructive fishing techniques like bottom trawling, dynamiting, and poisoning destroy habitats near shore as well as in the deep sea.
Tourism brings millions of boaters, snorkelers, and scuba divers into direct contact with fragile wetland and reef ecosystems. Container ships and tankers can damage habitat with their hulls and anchors. Spills of crude oil and other substances kill thousands of birds and fish and leave a toxic environment that can persist for years.
Perhaps the most devastating of all habitat-altering agents, however, is climate change. Scientists are still coming to grips with the consequences that excessive atmospheric carbon dioxide and Earth\’s rapid warming are having on ecosystems. But there is ample evidence indicating that the oceans are bearing the brunt of these changes.
As Earth\’s temperature rises, it is primarily the oceans that absorb the extra heat. Even small temperature changes can have far-reaching effects on the life cycles of marine animals from corals to whales.
In addition, warmer temperatures cause excess melting of ice caps and glaciers, raising sea levels and flooding estuaries.
High levels of atmospheric carbon dioxide, caused mainly by the burning of fossil fuels, are absorbed by the oceans, where the gas dissolves into carbonic acid. This elevated acidity inhibits the ability of marine animals, including many plankton organisms, to create shells, disrupting life within the very foundation of the ocean\’s food web.
Ongoing efforts to safeguard ocean habitats include the creation of gigantic marine sanctuaries where development is curtailed and fishing is prohibited. Laws banning the dumping of sewage and chemicals into the ocean and policies that foster better stewardship of wetlands are having positive effects. But scientists agree that drastic measures will be needed to avert the ocean crises being created by climate change.
Increasing Wildlife trade: We are currently experiencing an extinction crisis. Since 1970 the planet has lost 60 percent of its vertebrate wildlife populations,
leading the world’s foremost experts to warn that the annihilation of wildlife is now an emergency that threatens civilization. The United Nations Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Report concluded that one million species face extinction due to human causes, many within mere decades.
Globally, wildlife trade is the second-biggest threat to the vital biodiversity of our planet, following habitat loss. A recent study found that 958 species listed as at risk by the International Union for Conservation of Nature (IUCN) were in danger of extinction because they are being traded internationally. There are countless examples of species that have been decimated by wildlife trade, including elephants, rhinoceros, and pangolins.
This has devastating impacts not only on wildlife itself, but also on humans. In fact, many scientists assert that the destruction of nature is as dangerous to human life as climate change—and may threaten human life sooner than global warming—because it can result in cascading effects that reduce overall ecosystem functioning. Indeed, we depend on biodiversity, meaning a wide range of species existing together on the planet, for the healthy soil and crops that provide our food, the water we drink, the clean air we breathe, and the stability of weather patterns. An estimated four billion people also rely on natural medicines for their health care, medicines whose ingredients could be destroyed by a loss of biodiversity.
Illegal wildlife trade—what many refer to as “wildlife crime”—is also used to finance conflict and contribute to instability in countries that are already suffering. In Central African countries, such as the Democratic Republic of Congo, some armed groups raise funds by poaching and selling animals and lumber.
Destroying wildlife also has a severe economic impact on nations around the world. For example, logging and other forms of deforestation in Kenya threaten the country’s ability to grow tea, a product that brings in millions of dollars as an export industry.
Finally, the illegal wildlife trade spreads diseases and invasive alien species, which are plants and animals introduced by humans to areas outside their natural habitats. Both can have disastrous impacts on native wildlife and on humans. For example, smuggling animals across borders without proper inspection increases the risk of spreading diseases such as Ebola or bird flu. And the numbers of invasive alien species per country have risen by some 70 percent since 1970.Some examples will be better:
Demand for ivory in Asia and among antiques dealers around the world for its aesthetic uses, such as in carved decorative items, has decimated the elephant population. There were about 1.3 million elephants in Africa in 1979. By 1989, that number had plummeted to 600,000, a direct result of the animals being killed for their tusks. That same year, CITES effectively banned the international trade of ivory to save elephants from extinction. However, the population crashed again little more than two decades later, with 100,000 elephants killed between 2010 and 2012. This was due to approved one-off sales of ivory stockpiles from African to Asian countries in 2008: The more legal ivory on the market, the more opportunities there are for passing illegal ivory off as legal, thus the increase in poaching.
Rhino horns, touted to have medicinal powers, are among the most expensive substances on the planet. In reality, the protein that makes up rhino horn has no more potency than human fingernails, but its reputation, driving a wholesale market that may be worth a quarter of a billion dollars, has pushed the animals to the brink. All five species of rhinos are threatened with extinction, according to the IUCN, with four species listed as either endangered or critically endangered. Fortunately, rhinos are listed in CITES
Appendix I, meaning trade in their horns is banned, with the exception of South Africa’s and Eswatini’s (formerly Swaziland) southern white rhino populations, which are listed in Appendix II to allow trade in live animals. Despite the plight of the species, some countries continually seek authority to trade in rhino horn.
Pangolins, the scaly anteaters of Asia and Africa, are the most illegally traded mammal in the world. Indeed, a staggering one million pangolins are believed to have been taken from the wild over the past 15 years for their meat, which is consumed as a delicacy in Asian countries like China and Vietnam, and their scales, which are used in traditional medicines. In 2014, CITES voted unanimously to ban the international commercial trade in pangolins—all eight species of which are classified as threatened with extinction by the IUCN. However, despite the new Appendix I listing, the illegal trade continues, with seizures like a recent one in Singapore involving some 36,000 animals.
The historical impacts of human hunting on mammal populations has been well-documented. You only need to follow the timing of mammal extinction events to trace the footsteps of human arrival across the world’s continents. When we arrived, large mammals soon disappeared. The dramatic decline of whale populations over the 20th century as a result of hunting is another stark example: the Blue Whale was almost plunged into extinction, losing 99% of its numbers.
Let’s look at the recent and current threats that modern exploitation poses to the world’s mammals and birds. Overhunting is the leading threat to biodiversity. Across the tropics, an increasing number of areas can be described as “half-empty” or “empty” ecosystems – and the strongest predictor of these areas is not forest area, habitat type, or protection status. It’s the local patterns of hunting.
Many studies have documented large declines in wildlife populations due to overhunting. In a meta-analysis, published in the journal Science, Ana Benítez- López and colleagues assessed the impact of hunting on tropical bird and mammal populations.1 The meta-analysis included 176 studies, covering 97 bird and 254 mammal species. It found a 58% decline in bird, and 83% decline in mammal abundance in hunted versus unhunted areas. Another meta- analysis, published in Nature, focused on the impact of wildlife trade on mammal, bird and reptile populations. Oscar Morton and colleagues found a 62% decline in species abundance where wildlife trade was present.
Exploitation for bushmeat trade drove a 60% decline in populations.2
This decline in animal populations is pushing some species towards extinction. As I mentioned earlier, the Javan rhino was poached to extinction by its lucrative horn. Many others are facing the same fate. One-quarter of the world’s mammal species are threatened with extinction. In a study published in the Royal Society, William Ripple and colleagues estimated that bushmeat hunting was the primary threat for one-quarter (26%) of those at risk.3 That’s 301 terrestrial mammal species. All of them are in the tropics.
Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of the \”greenhouse effect\”1 — warming that results when the atmosphere traps heat radiating from Earth toward space.
Certain gases in the atmosphere block heat from escaping. Long-lived gases that remain semi-permanently in the atmosphere and do not respond physically or chemically to changes in temperature are described as \”forcing\” climate change. Gases, such as water vapor, which respond physically or chemically to changes in temperature are seen as \”feedbacks.\”
Gases that contribute to the greenhouse effect include:
Water vapor. The most abundant greenhouse gas, but importantly, it acts as a feedback to the climate. Water vapor increases as the Earth\’s atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect.
Carbon dioxide (CO2). A minor but very important component of the atmosphere, carbon dioxide is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land use changes, and burning fossil fuels. Humans have increased atmospheric CO2 concentration by 48% since the Industrial Revolution began. This is the most important long-lived \”forcing\” of climate change.
Methane. A hydrocarbon gas produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. On a molecule-for- molecule basis, methane is a far more active greenhouse gas than carbon dioxide, but also one which is much less abundant in the atmosphere.
Nitrous oxide. A powerful greenhouse gas produced by soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.
Chlorofluorocarbons (CFCs). Synthetic compounds entirely of industrial origin used in a number of applications, but now largely regulated in production and release to the atmosphere by international agreement for their ability to contribute to destruction of the ozone layer. They are also greenhouse gases.
Not enough greenhouse effect: The planet Mars has a very thin atmosphere, nearly all carbon dioxide. Because of the low atmospheric pressure, and with little to no methane or water vapor to reinforce the weak greenhouse effect, Mars has a largely frozen surface that shows no evidence of life.
Too much greenhouse effect: The atmosphere of Venus, like Mars, is nearly all carbon dioxide. But Venus has about 154,000 times as much carbon dioxide in its atmosphere as Earth (and about 19,000 times as much as Mars does), producing a runaway greenhouse effect and a surface temperature hot enough to melt lead.
Too much greenhouse effect: The atmosphere of Venus, like Mars, is nearly all carbon dioxide. But Venus has about 154,000 times as much carbon dioxide in its atmosphere as Earth (and about 19,000 times as much as Mars does), producing a runaway greenhouse effect and a surface temperature hot enough to melt lead.
On Earth, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2. To a lesser extent, the clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases.
The consequences of changing the natural atmospheric greenhouse are difficult to predict, but some effects seem likely:
On average, Earth will become warmer. Some regions may welcome warmer temperatures, but others may not.
Warmer conditions will probably lead to more evaporation and precipitation overall, but individual regions will vary, some becoming wetter and others dryer.
A stronger greenhouse effect will warm the ocean and partially melt glaciers and ice sheets, increasing sea level. Ocean water also will expand if it warms, contributing further to sea level rise.
Outside of a greenhouse, higher atmospheric carbon dioxide (CO2) levels can have both positive and negative effects on crop yields. Some laboratory experiments suggest that elevated CO2 levels can increase plant growth.
However, other factors, such as changing temperatures, ozone, and water and nutrient constraints, may more than counteract any potential increase in yield. If optimal temperature ranges for some crops are exceeded, earlier possible gains in yield may be reduced or reversed altogether.
Climate extremes, such as droughts, floods and extreme temperatures, can lead to crop losses and threaten the livelihoods of agricultural producers and the food security of communities worldwide. Depending on the crop and ecosystem, weeds, pests, and fungi can also thrive under warmer temperatures, wetter climates, and increased CO2 levels, and climate change will likely increase weeds and pests.
Finally, although rising CO2 can stimulate plant growth, research has shown that it can also reduce the nutritional value of most food crops by reducing the concentrations of protein and essential minerals in most plant species. Climate change can cause new patterns of pests and diseases to emerge, affecting plants, animals and humans, and posing new risks for food security, food safety and human health.2
Next talkings will be in part 2….
(To be continued)