If an introduced species is able to survive in its new habitat, that introduction is now reflected in the observed range of the species. Exotic threats : The brown tree snake, Boiga irregularis, is an exotic species that has caused numerous extinctions on the island of Guam since its accidental introduction in Most exotic species introductions probably fail because of the low number of individuals introduced or poor adaptation to the ecosystem they enter.
Some species, however, possess preadaptations that can make them especially successful in a new ecosystem. These exotic species often undergo dramatic population increases in their new habitat, resetting the ecological conditions in the new environment, while threatening the species that exist there.
For this reason, exotic species, also called invasive species, can threaten other species through competition for resources, predation, or disease. Invasive species can change the functions of ecosystems.
For example, invasive plants can alter the fire regimen, nutrient cycling, and hydrology in native ecosystems. Invasive species that are closely related to rare native species have the potential to hybridize with the native species. Harmful effects of hybridization have led to a decline and even extinction of native species. For example, hybridization with introduced cordgrass, Spartina alterniflora , threatens the existence of California cordgrass in San Francisco Bay.
Invasive species cause competition for native species. Four hundred of the endangered species under the Endangered Species Act are at risk due to this competition.
Global decline in amphibian species : This Limosa Harlequin Frog Atelopus limosus , an endangered species from Panama, died from a fungal disease called chytridiomycosis. The red lesions are symptomatic of the disease. Lakes and islands are particularly vulnerable to extinction threats from introduced species.
In Lake Victoria, as mentioned earlier, the intentional introduction of the Nile perch was largely responsible for the extinction of about species of cichlids. The accidental introduction of the brown tree snake via aircraft from the Solomon Islands to Guam in has led to the extinction of three species of birds and three to five species of reptiles endemic to the island. Several other species are still threatened. The brown tree snake is adept at exploiting human transportation as a means to migrate; one was even found on an aircraft arriving in Corpus Christi, Texas.
Constant vigilance on the part of airport, military, and commercial aircraft personnel is required to prevent the snake from moving from Guam to other islands in the Pacific, especially Hawaii. Islands do not make up a large area of land on the globe, but they do contain a disproportionate number of endemic species because of their isolation from mainland ancestors.
It now appears that the global decline in amphibian species recognized in the s is, in some part, caused by the fungus Batrachochytrium dendrobatidis , which causes the disease chytridiomycosis. There is evidence that the fungus, native to Africa, may have been spread throughout the world by transport of a commonly-used laboratory and pet species: the African clawed toad Xenopus laevis.
It may well be that biologists themselves are responsible for spreading this disease worldwide. The North American bullfrog, Rana catesbeiana , which has also been widely introduced as a food animal, but which easily escapes captivity, survives most infections of Batrachochytriumdendrobatidis and can act as a reservoir for the disease.
The global warming trend is recognized as a major biodiversity threat, especially when combined with other threats such as habitat loss. Climate change, specifically, the anthropogenic caused by humans warming trend presently underway, is recognized as a major extinction threat, particularly when combined with other threats such as habitat loss. Scientists disagree about the probable magnitude of the effects, with extinction rate estimates ranging from 15 percent to 40 percent of species by Scientists do agree, however, that climate change will alter regional climates, including rainfall and snowfall patterns, making habitats less hospitable to the species living in them.
Grizzly-polar bear hybrid : Since , grizzly bears Ursus arctos horribilis have been spotted farther north than their historic range, a possible consequence of climate change.
As a result, grizzly bear habitat now overlaps polar bear Ursus maritimus habitat. The two kinds of bears, which are capable of mating and producing viable offspring, are considered separate species as historically they lived in different habitats and never met. However, in a hunter shot a wild grizzly-polar bear hybrid known as a grolar bear, the first wild hybrid ever found.
The warming trend will shift colder climates toward the north and south poles, forcing species to move with their adapted climate norms while facing habitat gaps along the way. The shifting ranges will impose new competitive regimes on species as they find themselves in contact with other species not present in their historic range. One such unexpected species contact is between polar bears and grizzly bears. Previously, these two species had separate ranges.
Now, with their ranges are overlapping, there are documented cases of these two species mating and producing viable offspring. Many contemporary mismatches to shifts in resource availability and timing have recently been documented. Range shifts are already being observed. The same study suggests that the optimal shift based on warming trends was double that distance, suggesting that the populations are not moving quickly enough. Range shifts have also been observed in plants, butterflies, other insects, freshwater fishes, reptiles, and mammals.
Climate gradients will also move up mountains, eventually crowding species higher in altitude and eliminating the habitat for those species adapted to the highest elevations. Some climates will completely disappear. The rate of warming appears to be accelerated in the arctic, which is recognized as a serious threat to polar bear populations that require sea ice to hunt seals during the winter months; seals are the only source of protein available to polar bears.
A trend to decreasing sea ice coverage has occurred since observations began in the mid-twentieth century. The rate of decline observed in recent years is far greater than previously predicted by climate models.
Finally, global warming will raise ocean levels due to glacial melt and the greater volume of warmer water. Shorelines will be inundated, reducing island size, which will have an effect on many species; a number of islands will disappear entirely. Additionally, the gradual melting and subsequent refreezing of the poles, glaciers, and higher elevation mountains, a cycle that has provided freshwater to environments for centuries, will also be jeopardized.
UN Environment is proud to support the Global Assessment Report produced by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services because it highlights the critical need to integrate biodiversity considerations in global decision-making on any sector or challenge, whether its water or agriculture, infrastructure or business.
The magic of seeing fireflies flickering long into the night is immense. We draw energy and nutrients from nature. We find sources of food, medicine, livelihoods and innovation in nature. Our well-being fundamentally depends on nature. Our efforts to conserve biodiversity and ecosystems must be underpinned by the best science that humanity can produce. Our local, indigenous and scientific knowledge are proving that we have solutions and so no more excuses: we must live on earth differently.
UNESCO is committed to promoting respect of the living and of its diversity, ecological solidarity with other living species, and to establish new, equitable and global links of partnership and intragenerational solidarity, for the perpetuation of humankind. Healthy biodiversity is the essential infrastructure that supports all forms of life on earth, including human life.
It also provides nature-based solutions on many of the most critical environmental, economic, and social challenges that we face as human society, including climate change, sustainable development, health, and water and food security. We are currently in the midst of preparing for the UN Biodiversity Conference, in China, which will mark the close of the Aichi Biodiversity Targets and set the course for a post ecologically focused sustainable development pathway to deliver multiple benefits for people, the planet and our global economy.
I want to extend my thanks and congratulations to the IPBES community for their hard work, immense contributions and continued partnership. Together, assessments undertaken by IPBES, FAO, CBD and other organizations point to the urgent need for action to better conserve and sustainably use biodiversity and to the importance of cross-sectoral and multidisciplinary collaboration among decision-makers and other stakeholders at all levels.
You must be logged in to post a comment. Current global response insufficient;. Further Information on Key Issues from the Report Scale of Loss of Nature Gains from societal and policy responses, while important, have not stopped massive losses. Since , trends in agricultural production, fish harvest, bioenergy production and harvest of materials have increased, in response to population growth, rising demand and technological development, this has come at a steep price, which has been unequally distributed within and across countries.
The pace of agricultural expansion into intact ecosystems has varied from country to country. Losses of intact ecosystems have occurred primarily in the tropics, home to the highest levels of biodiversity on the planet. Plants Through photosynthesis, plants provide the oxygen we breathe and the food we eat and are thus the foundation of most life on Earth. They're also the source of a majority of medicines in use today. Of the more than , known species of plants, the IUCN has evaluated only 12, species, finding that about 68 percent of evaluated plant species are threatened with extinction.
Unlike animals, plants can't readily move as their habitat is destroyed, making them particularly vulnerable to extinction. Global warming is likely to substantially exacerbate this problem. Already, scientists say, warming temperatures are causing quick and dramatic changes in the range and distribution of plants around the world. With plants making up the backbone of ecosystems and the base of the food chain, that's very bad news for all species, which depend on plants for food, shelter, and survival.
Elizabeth Hadly of Stanford University reveals how human activities have caused the extinctions of many species in the past and the present. Human population growth is driving habitat destruction and climate change, both direct threats to biodiversity. Reptiles Globally, 21 percent of the total evaluated reptiles in the world are deemed endangered or vulnerable to extinction by the IUCN — species — while in the United States, 32 reptile species are at risk, about 9 percent of the total.
Island reptile species have been dealt the hardest blow, with at least 28 island reptiles having died out since The main threats to reptiles are habitat destruction and the invasion of nonnative species, which prey on reptiles and compete with them for habitat and food. Of some 6, plant species cultivated for food, fewer than contribute substantially to global food output, and only nine account for 66 percent of total crop production.
Of the 7, local occurring in one country breeds of livestock reported globally, 26 percent are at risk of extinction. Nearly a third of fish stocks are overfished, more than half have reached their sustainable limit. Information from the 91 reporting countries reveals that wild food species and many species that contribute to ecosystem services that are vital to food and agriculture, including pollinators, soil organisms and natural enemies of pests, are rapidly disappearing.
For example, countries report that 24 percent of nearly 4, wild food species — mainly plants, fish and mammals - are decreasing in abundance. But the proportion of wild foods in decline is likely to be even greater as the state of more than half of the reported wild food species is unknown. From desert to Grasslands A fifth of the land on our planet is covered by desert.
The driest of all is the Atacama in South America. There are places there where rain has never been recorded. Deserts may to appear to be barren and empty, but they are of crucial importance to life. For those that can overcome their challenges, they provide a vital refuge. Species that live there, the Socotran Cormorants, currently Deserts cannot support large numbers of animals the year round, and even those specially adapted to these conditions can only survive in small numbers.
But on very special occasions, deserts are transformed. Once in a decade there may be a cloudburst. A single one can turn the desert green. In Southern California the change is visible from space. Hundreds of square kilometers suddenly bloom. If such transformations become regular, a new habitat may develop. They support the greatest aggregations of large animals on Earth. The Serengeti sustains herds of over a million wildebeest.
They follow the rains to crop the newly sprung grass. These vast herds attract predators, like the cheetah. The regulation of wildebeest by the cheetah can continue because the Serengeti is protected, and has been for over 65 years. But the Serengeti is an exception.
Across the planet, space for grasslands has been steadily disappearing. A hundred and eighty years ago, herds of bison, millions strong, grazed the Great Plains of North America. They roamed across a prairie a hundred times larger than the Serengeti. This was the true wild west. Today, most of the prairie is silent. Humans slaughtered the great herds.
Less than Exactly how many species rain forests contain is unknown, but it runs into millions. And new ones are discovered every week. There are a number of issues threatening our planet's biodiversity, from climate change to invasive species. Below, we discuss some of the biggest threats facing biodiversity today, as well as what the world can do and is doing to keep them in check.
How do humans negatively affect biodiversity? Our actions in a given environment cause problems directly and indirectly. Climate change Changes in climate throughout our planet's history have, of course, altered life on Earth in the long run — ecosystems have come and gone and species routinely go extinct.
But rapid, manmade climate change speeds up the process, without affording ecosystems and species the time to adapt. For example, rising ocean temperatures and diminishing Arctic sea ice affects marine biodiversity and can shift vegetation zones, having global implications.
Overall, climate is a major factor in the distribution of species across the globe; climate change forces them to adjust. But many are not able to cope, causing them to die out. Deforestation and habitat loss Deforestation is a direct cause of extinction and loss of biodiversity.
An estimated 18 million acres of forest are lost each year, due in part to logging and other human practices, destroying the ecosystems on which many species depend.
Tropical rainforests in particular, such as the Amazon, hold a high percentage of the world's known species, yet the regions themselves are in decline due to humans. Overexploitation Overhunting, overfishing and over-harvesting contribute greatly to the loss of biodiversity, killing off numerous species over the past several hundred years. Poaching and other forms of hunting for profit increase the risk of extinction; the extinction of an apex predator — or, a predator at the top of a food chain — can result in catastrophic consequences for ecosystems.
Invasive species The introduction of non-native species into an ecosystem can threaten endemic wildlife either as predators or competing for resources , affect human health and upset economies.
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