This article has multiple issues. Please help improve it or discuss these issues on the talk page . (Learn how and when to remove these messages)
|
An ecological or environmental crisis occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
The evolutionary theory of punctuated equilibrium sees infrequent ecological crises as a potential driver of rapid evolution.
Because of the impact of humans on the natural environment in the recent geological period, the term ecological crisis is often applied to environmental issues caused by human civilizations such as: the climate crisis, biodiversity loss and plastic pollution which have emerged as major global challenges during the first few decades of the 21st century.
Climate change is starting to have major impacts on ecosystems. With global temperature rising, there is a decrease in snow-fall, and sea levels are rising. Ecosystems will change or evolve to cope with the increase in temperature. Consequently, many species are being driven out of their habitats.
Polar bears are being threatened. They need ice for hunting seals, their primary prey. However, the ice caps are melting, making their hunting periods shorter each year. As a result, the polar bears are not developing enough fat for the winter; therefore, they are not able to reproduce at a healthy rate.
Fresh water and wetland ecosystems are dealing with extreme effects of the increase of temperature. The climate change could be devastating to salmon and trout and to other aquatic life. The increase in temperature will disrupt the current life patterns of the salmon and trout. The cold-water fish will eventually leave their natural geographical range to live in cooler waters by migrating to higher elevations.
While many species have been able to adapt to the new conditions by moving their range further towards the poles, other species are not as fortunate. The option to move is not available for polar bears and for some aquatic life.
Climate change is already now altering biomes, adversely affecting terrestrial and marine ecosystems. [2] [3] Climate change represents long-term changes in temperature and average weather patterns. [4] [5] This leads to a substantial increase in both the frequency and the intensity of extreme weather events. [6] As a region's climate changes, a change in its flora and fauna follows. [7] For instance, out of 4000 species analyzed by the IPCC Sixth Assessment Report, half were found to have shifted their distribution to higher latitudes or elevations in response to climate change. [8]
Furthermore, climate change may cause ecological disruption among interacting species, via changes in behaviour and phenology, or via climate niche mismatch. [9] For example, climate change can cause species to move in different directions, potentially disrupting their interactions with each other. [10] [11]
Examples of effects on some biome types are provided in the following.[ clarification needed ][ where? ] Research into desertification is complex, and there is no single metric which can define all aspects. However, more intense climate change is still expected to increase the current extent of drylands on the Earth's continents. Most of the expansion will be seen over regions such as "southwest North America, the northern fringe of Africa, southern Africa, and Australia". [12]
Mountains cover approximately 25 percent of the Earth's surface and provide a home to more than one-tenth of the global human population. Changes in global climate pose a number of potential risks to mountain habitats. [13]
Boreal forests, also known as taiga, are warming at a faster rate than the global average, [14] leading to drier conditions in the Taiga, which leads to a whole host of subsequent impacts. [15] Climate change has a direct impact on the productivity of the boreal forest, as well as its health and regeneration. [15]
Almost no other ecosystem is as vulnerable to climate change as coral reefs. Updated 2022 estimates show that even at a global average increase of 1.5 °C (2.7 °F) over pre-industrial temperatures, only 0.2% of the world's coral reefs would still be able to withstand marine heatwaves, as opposed to 84% being able to do so now, with the figure dropping to 0% at 2 °C (3.6 °F) warming and beyond. [16] [17]Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in biological diversity in a given area. The decrease can be temporary or permanent. It is temporary if the damage that led to the loss is reversible in time, for example through ecological restoration. If this is not possible, then the decrease is permanent. The cause of most of the biodiversity loss is, generally speaking, human activities that push the planetary boundaries too far. [18] [19] [20] These activities include habitat destruction [21] (for example deforestation) and land use intensification (for example monoculture farming). [22] [23] Further problem areas are air and water pollution (including nutrient pollution), over-exploitation, invasive species [24] and climate change. [21]
Many scientists, along with the Global Assessment Report on Biodiversity and Ecosystem Services , say that the main reason for biodiversity loss is a growing human population because this leads to human overpopulation and excessive consumption. [25] [26] [27] [28] [29] Others disagree, saying that loss of habitat is caused mainly by "the growth of commodities for export" and that population has very little to do with overall consumption. More important are wealth disparities between and within countries. [30]
Climate change is another threat to global biodiversity. [31] [32] For example, coral reefs—which are biodiversity hotspots—will be lost by the year 2100 if global warming continues at the current rate. [33] [34] Still, it is the general habitat destruction (often for expansion of agriculture), not climate change, that is currently the bigger driver of biodiversity loss. [35] [36] Invasive species and other disturbances have become more common in forests in the last several decades. These tend to be directly or indirectly connected to climate change and can cause a deterioration of forest ecosystems. [37] [38]
Groups that care about the environment have been working for many years to stop the decrease in biodiversity. Nowadays, many global policies include activities to stop biodiversity loss. For example, the UN Convention on Biological Diversity aims to prevent biodiversity loss and to conserve wilderness areas. However, a 2020 United Nations Environment Programme report found that most of these efforts had failed to meet their goals. [39] For example, of the 20 biodiversity goals laid out by the Aichi Biodiversity Targets in 2010, only six were "partially achieved" by 2020. [40] [41]
This ongoing global extinction is also called the holocene extinction or sixth mass extinction.In the wilderness, the problem of animal overpopulation is solved by predators. Predators tend to look for signs of weakness in their prey, and therefore usually first eat the old or sick animals. This has the side effects of ensuring a strong stock among the survivors and controlling the population.
In the absence of predators, animal species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation. In fact, an abundant supply of resources can produce a population boom that ends up with more individuals than the environment can support. In this case, starvation, thirst, and sometimes violent competition for scarce resources may effect a sharp reduction in population, and in a very short lapse, a population crash. Lemmings, as well as other less popular species of rodents, are known to have such cycles of rapid population growth and subsequent decrease.
In an ideal setting, when animal populations grow, so do the number of predators that feed on that particular animal. Animals that have birth defects or weak genes (such as the runt of the litter) also die off, unable to compete over food with stronger, healthier animals.
In reality, an animal that is not native to an environment may have advantages over the native ones, such being unsuitable for the local predators. If left uncontrolled, such an animal can quickly overpopulate and ultimately destroy its environment.
Examples of animal overpopulation caused by introduction of a foreign species abound.
Some common examples of ecological crises are:
The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event caused by humans during the Holocene epoch. These extinctions span numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, and affecting not just terrestrial species but also large sectors of marine life. With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates and is increasing. During the past 100–200 years, biodiversity loss and species extinction have accelerated, to the point that most conservation biologists now believe that human activity has either produced a period of mass extinction, or is on the cusp of doing so. As such, after the "Big Five" mass extinctions, the Holocene extinction event has also been referred to as the sixth mass extinction or sixth extinction; given the recent recognition of the Capitanian mass extinction, the term seventh mass extinction has also been proposed for the Holocene extinction event.
Biodiversity is the variety and variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth. It is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa.
Extinction is the termination of a taxon by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence.
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences, and the practice of natural resource management.
Habitat conservation is a management practice that seeks to conserve, protect and restore habitats and prevent species extinction, fragmentation or reduction in range. It is a priority of many groups that cannot be easily characterized in terms of any one ideology.
The Anthropocene was a rejected proposal for a geological epoch following the Holocene, dating from the commencement of significant human impact on Earth up to the present day. This impact affects Earth's oceans, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen for example in biodiversity loss and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution, to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term. However, in 2024 the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) rejected the Anthropocene Epoch proposal for inclusion in the Geologic Time Scale sparking significant disagreement from scientists working in the field.
Environmental degradation is the deterioration of the environment through depletion of resources such as: quality of air, water and soil, the destruction of ecosystems, habitat destruction, the extinction of wildlife, and pollution. It is defined as any change or disturbance to the environment perceived to be deleterious or undesirable. The environmental degradation process amplifies the impact of environmental issues which leave lasting impacts on the environment.
Habitat destruction occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved to elsewhere or are dead, leading to a decrease in biodiversity and species numbers. Habitat destruction is in fact the leading cause of biodiversity loss and species extinction worldwide.
Human impact on the environment refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society is causing severe effects including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Some human activities that cause damage to the environment on a global scale include population growth, neoliberal economic policies and rapid economic growth, overconsumption, overexploitation, pollution, and deforestation. Some of the problems, including global warming and biodiversity loss, have been proposed as representing catastrophic risks to the survival of the human species.
Wildlife conservation refers to the practice of protecting wild species and their habitats in order to maintain healthy wildlife species or populations and to restore, protect or enhance natural ecosystems. Major threats to wildlife include habitat destruction, degradation, fragmentation, overexploitation, poaching, pollution, climate change, and the illegal wildlife trade. The IUCN estimates that 42,100 species of the ones assessed are at risk for extinction. Expanding to all existing species, a 2019 UN report on biodiversity put this estimate even higher at a million species. It is also being acknowledged that an increasing number of ecosystems on Earth containing endangered species are disappearing. To address these issues, there have been both national and international governmental efforts to preserve Earth's wildlife. Prominent conservation agreements include the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the 1992 Convention on Biological Diversity (CBD). There are also numerous nongovernmental organizations (NGO's) dedicated to conservation such as the Nature Conservancy, World Wildlife Fund, and Conservation International.
There are several plausible pathways that could lead to an increased extinction risk from climate change. Every plant and animal species has evolved to exist within a certain ecological niche. But climate change leads to changes of temperature and average weather patterns. These changes can push climatic conditions outside of the species' niche, and ultimately render it extinct. Normally, species faced with changing conditions can either adapt in place through microevolution or move to another habitat with suitable conditions. However, the speed of recent climate change is very fast. Due to this rapid change, for example cold-blooded animals may struggle to find a suitable habitat within 50 km of their current location at the end of this century.
A wild fishery is a natural body of water with a sizeable free-ranging fish or other aquatic animal population that can be harvested for its commercial value. Wild fisheries can be marine (saltwater) or lacustrine/riverine (freshwater), and rely heavily on the carrying capacity of the local aquatic ecosystem.
Global biodiversity is the measure of biodiversity on planet Earth and is defined as the total variability of life forms. More than 99 percent of all species that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 2 million to 1 trillion, but most estimates are around 11 million species or fewer. About 1.74 million species were databased as of 2018, and over 80 percent have not yet been described. The total amount of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at 5.0 x 1037, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).
There is an ongoing decline in plant biodiversity, just like there is ongoing biodiversity loss for many other life forms. One of the causes for this decline is climate change. Environmental conditions play a key role in defining the function and geographic distributions of plants. Therefore, when environmental conditions change, this can result in changes to biodiversity. The effects of climate change on plant biodiversity can be predicted by using various models, for example bioclimatic models.
Overpopulation or overabundance is a phenomenon in which a species' population becomes larger than the carrying capacity of its environment. This may be caused by increased birth rates, lowered mortality rates, reduced predation or large scale migration, leading to an overabundant species and other animals in the ecosystem competing for food, space, and resources. The animals in an overpopulated area may then be forced to migrate to areas not typically inhabited, or die off without access to necessary resources.
Defaunation is the global, local, or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.
Environmental issues are disruptions in the usual function of ecosystems. Further, these issues can be caused by humans or they can be natural. These issues are considered serious when the ecosystem cannot recover in the present situation, and catastrophic if the ecosystem is projected to certainly collapse.
Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in biological diversity in a given area. The decrease can be temporary or permanent. It is temporary if the damage that led to the loss is reversible in time, for example through ecological restoration. If this is not possible, then the decrease is permanent. The cause of most of the biodiversity loss is, generally speaking, human activities that push the planetary boundaries too far. These activities include habitat destruction and land use intensification. Further problem areas are air and water pollution, over-exploitation, invasive species and climate change.
An ecosystem, short for ecological system, is defined as a collection of interacting organisms within a biophysical environment. Ecosystems are never static, and are continually subject to both stabilizing and destabilizing processes. Stabilizing processes allow ecosystems to adequately respond to destabilizing changes, or perturbations, in ecological conditions, or to recover from degradation induced by them: yet, if destabilizing processes become strong enough or fast enough to cross a critical threshold within that ecosystem, often described as an ecological 'tipping point', then an ecosystem collapse. occurs.
The Global Assessment Report on Biodiversity and Ecosystem Services is a report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, on the global state of biodiversity. A summary for policymakers was released on 6 May 2019. The report states that, due to human impact on the environment in the past half-century, the Earth's biodiversity has suffered a catastrophic decline unprecedented in human history, as an estimated 82 percent of wild mammal biomass has been lost. The report estimates that there are 8 million animal and plant species on Earth, with the majority represented by insects. Out of those 8 million species, 1 million are threatened with extinction, including 40 percent of amphibians, almost a third of reef-building corals, more than a third of marine mammals, and 10 percent of all insects.
Moreover, we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century.
For the first time at a global scale, the report has ranked the causes of damage. Topping the list, changes in land use—principally agriculture—that have destroyed habitat. Second, hunting and other kinds of exploitation. These are followed by climate change, pollution, and invasive species, which are being spread by trade and other activities. Climate change will likely overtake the other threats in the next decades, the authors note. Driving these threats are the growing human population, which has doubled since 1970 to 7.6 billion, and consumption. (Per capita of use of materials is up 15% over the past 5 decades.)
The overarching driver of species extinction is human population growth and increasing per capita consumption.
Conservation biologists standardly list five main direct drivers of biodiversity loss: habitat loss, overexploitation of species, pollution, invasive species, and climate change. The Global Assessment Report on Biodiversity and Ecosystem Services found that in recent decades habitat loss was the leading cause of terrestrial biodiversity loss, while overexploitation (overfishing) was the most important cause of marine losses (IPBES, 2019). All five direct drivers are important, on land and at sea, and all are made worse by larger and denser human populations.
Research suggests that the scale of human population and the current pace of its growth contribute substantially to the loss of biological diversity. Although technological change and unequal consumption inextricably mingle with demographic impacts on the environment, the needs of all human beings—especially for food—imply that projected population growth will undermine protection of the natural world.
Current generic extinction rates will likely greatly accelerate in the next few decades due to drivers accompanying the growth and consumption of the human enterprise such as habitat destruction, illegal trade, and climate disruption.
Through examining the drivers of biodiversity loss in highly biodiverse countries, we show that it is not population driving the loss of habitats, but rather the growth of commodities for export, particularly soybean and oil-palm, primarily for livestock feed or biofuel consumption in higher income economies.