Intervention in the Ecosystem - Essay Example

Overview There has been growing fear between many scientists that human interferences are modifying the capa of ecosystems to endow with their goods (e.g. freshwater, food, pharmaceutical products, etc) and services (e.g. purification of air, water, soil, sequestration of pollutants, etc). This can lead to ecosystem disorder and bear a significant impact on humans and animals as well as plants, in a variety of ways and through complex pathways. These are moreover modified by the population's existing vulnerability and their future capacity to execute adjustment measures. Because of these concerns, the prominent changes, at least many of it, occur so in the arctic region. The basis for this is strong positive feedback associated with occurs with ice and snow melt. As a fact, ice and snow are highly reflective and white, for this reason, when the ground or ocean beneath is revealed more absorption occurs. This leads to further warmingfurther melting etc Clearly the level of warming currently occurring in the arctic is having an enormous impact on the region and the magnitude of further warming is set to be disastrous for the region. Thus, the Arctic Climate Impact Assessment (ACIA) states: "The reduction in sea ice is very likely to have devastating consequences for polar bears, ice-dependant seals, and local people for whom these animals are the primary source of food." Introduction The polar bear (Ursus maritimus) is the world's largest species of bear and the largest land predator. There is a great difference in size between male and female polar bears, with the males (350-800 kg) weighing more than twice as much as the females (150-300 kg). Their body weight varies considerably during the season - especially female bears which can often double in weight between early spring and late summer. Compared to other bear species, the polar bear has a relatively small, long and narrow head, smaller and shorter fur-covered ears, and shorter, more powerful claws. Its longer predatory teeth and sharper molars have helped polar bears adapt to the arctic climate and its almost exclusively carnivorous lifestyle. The polar bear is the youngest species of bear and is closely related to the brown bear (Ursus arctos) and grizzly bear (Ursus arctos horribilis). In the wild, polar bears normally live to be 20-30 years old. Both males and females mature at the age of four to five years. Females often give birth to their first litter of cubs when they reach maturity, while males do not usually start mating until they are between eight to ten years old. Mating takes place in April-May, but delayed implantation (the fertilised egg stops developing at an early stage) means that foetal development does not commence until September-October. During late autumn, females go into hibernation and remain there for approximately four months. At about the beginning of January, between one and three cubs are born (depending on the mother's age and condition). The newborn cubs are extremely small, weighing only about half a kilo, but they grow rapidly due to the high fat content of their mother's milk. The cubs stay with the mother until they are two-and-a-half years old. The cub infant mortality rate is high and can exceed 70%. Only about a third of cubs reach the age of two. The polar bear is a circumpolar species and is found in arctic regions where there is access to sea ice throughout much of the year. Polar bear populations are found in Canada, Alaska (USA), Greenland, the Russian Arctic, the Norwegian Arctic and on the ice surrounding the North Pole. The global population of polar bears consists of roughly 20,000-25,000 individuals spread between 19 sub-populations. However, polar bears wander across enormous distances, so there are no major genetic differences between these populations. The distribution of polar bears in their habitat is far from even and is highly dependent on the availability of their prey. In the central areas of the polar icecap there is only very limited access to prey, and the density of polar bear populations is thus considerably lower there than in the productive areas in the bordering zones. Concepts and Values of Biodiversity The term biological diversity', often shortened to biodiversity', is an umbrella term used to describe the number, variety and variability of living organisms in a given assemblage. Biodiversity therefore embraces the whole of Life on Earth'. Decline in biodiversity includes all those changes that have to do with reducing or simplifying biological heterogeneity, from individuals to regions (Wadhams, 2000). This is a more subtle definition than the global stock of biological resources, a more anthropocentric term for biota such as forests, wetlands and marine habitats. Biological resources are simply those components of biodiversity which maintain current or potential human uses. They represent the diversity about which most is known. This anthropocentric view of biological resources offers a convenient window' for analysis over alternative value paradigms such as intrinsic value': values in themselves and, nominally anyway, unrelated to human use. Intrinsic values are relevant to conservation decisions, but they are generally not measurable. As such they do not help to define actions in the context where choices have to be made against the backdrop of scarce conservation funds. The Meaning of Biological Diversity Biodiversity may be described in terms of genes, species, and ecosystems, corresponding to three fundamental and hierarchically-related levels of biological organization. Genetic diversity Genetic diversity is the sum of genetic information contained in the genes of individuals of plants, animals and micro-organisms. Each species is the repository of an immense amount of genetic information. Species diversity Species are regarded as populations within which gene flow occurs under natural conditions. Within a species, all normal individuals are capable of breeding with the other individuals of the opposite sex belonging to the same species, or at least they are capable of being genetically linked with them through chains of other breeding individuals. By definition, members of one species do not breed freely with members of other species. Although this definition works well for many animal and plant species, it is more difficult to delineate species in populations where hybridization, or self-fertilization or parthenogenesis occurs. Arbitrary divisions must be made, and indeed this is an area where scientists often disagree. Ecosystem diversity Ecosystem diversity relates to the variety of habitats, biotic communities and ecological processes in the biosphere as well as the diversity within ecosystems. Diversity can be described at a number of different levels and scales: - Functional diversity is the relative abundance of functionally different kinds of organisms. - Community diversity is the number sizes and spatial distribution of communities, and is sometimes referred to as patchiness. - Landscape diversity is the diversity of scales of patchiness. There is no simple relationship within any ecosystem between a change in its diversity and the resulting change in the system's processes. For example, the loss of a species from a particular area or region (local extinction or extirpation) may have little or no effect on net primary productivity if competitors take its place in the community. The converse may be true in other cases. Influence of Current Climatic Regimes The sea ice of the Arctic Ocean and the connected frozen seas is home to the largest and most predatory of the bear family. All bears alive today evolved 22 million years ago from a common ancestor - the Ursavus of Asia. Polar bears (Ursus maritimus) evolved from a group of brown bears (Ursus arctos) over 200,000 years ago, which became isolated from other brown bear populations by glaciers, possibly in Siberia. It is easy to imagine the evolutionary change in brown bears that inhabited a northern coast during a climatic cooling period, when food as tempting as unwary seal pups can be found offshore. Adaptations and evolution Polar bears evolved rapidly to adapt to their niche. In a case of quantum evolution, polar bears evolved rapidly to exploit a vacant ecological niche as a specialized predator of seals. The rapid changes from a brown bear to a polar bear include these (Talbot and Shields, 1996): white-yellow fur that helps them meld into their background as they sneak up on their prey claws that are catlike, an adaptation to grasp fleeing prey feet that are heavily furred to provide warmth smaller ears to avoid freezing in the frigid winters a narrower and more elongated skull, an adaptation perhaps to warm cold inhaled air, to aid the sense of smell, or to assist with the capture of prey trying to slip through a narrow opening to the safety of the sea below the ability to enter a fasting physiological state at any time of the year, unlike other bears, which enter this state only during winter torpor only four mammae (unlike brown bears with six) and a smaller litter size, an adaptation to the harsh environment for raising young Their range has been constant in the last few 100 years. Living and dying on the sea ice is not conducive to creating a good fossil record, but polar bears existed in Europe during the last ice age, and fossil remains have been found in Germany, Sweden, Denmark, Norway, and England Stirling et al, 2008). Polar bears were present in Scandinavia as recently as 10,660 years ago. Unlike most large carnivores, the current distribution of polar bears is similar to that of the last few hundred years. No subspecies of polar bears are recognized. Diet and feeding strategy Polar bears eat meat exclusively (Stanley, 1979). The lifestyle of polar bears is dramatically different from their brown bear ancestors. Despite their brief evolutionary separation, these two species exploit vastly different energy sources. Arctic brown bears are terrestrial, and most of their diet is vegetation augmented by animal protein. Polar bears, in contrast, are the most carnivorous of the bears, and two species of seals make up the bulk of their diet: The ringed seal (Phoca hispida), reaching over 60 kg and the most numerous seal in the Arctic, is their main prey. The larger bearded seal (Erignathus barbatus), which can top 400 kg, is also commonly taken. Both of these seals rely on sea ice to reproduce and molt, and neither species is found where sea ice is absent. Polar bears are opportunistic and will exploit food sources from both marine and terrestrial sources. Seals, however, are what make the life history of the polar bear possible. Seals are their primary source of food (Smith, 1980). The fat-laden seals that polar bears eat allow them to grow larger than most brown bears. Being large is an advantage for staying warm in cold climates. More importantly, during the spring and early summer, polar bears gorge themselves on nave newborn and recently weaned seal pups and deposit a thick fat layer that allows the bears to go through extended periods without food. Seals are an abundant food source that is converted into a portable energy store. Pregnant female polar bears in Hudson Bay can fast for up to 8 months and rear offspring (usually two) to about 10 kg before returning to the sea ice to feed on seals. Bears can double, triple, or quadruple their body mass during the spring. In contrast to brown bears, only pregnant female polar bears enter dens over winter; all other polar bears brave the harsh winter conditions trying to find a few seals to stem the loss of their precious fat stores. Habitat Polar bears need sea ice to hunt and breed. The sea ice is a dynamic habitat that undergoes huge annual variation in distribution and character. Polar bears follow the temporal shifts in habitats to access their prey. Annual sea ice, ice that forms and then melts within a single year, is the primary habitat of polar bears and is used various ways (Rehger et al, 2007): as a platform to hunt as the habitat for mating for travel, migration, and connecting habitats as a summer refuge to den and produce young in some areas, primarily in Alaska They travel huge distances to find food. In response to the extreme variation in ice, female polar bears can cover huge areas in a single year, with many bears wandering over 200,000 km2 of sea ice (Lindsay and Zhang, 2005). In contrast, brown bears use areas that are a tiny fraction of what polar bears use; a polar bear home range can be well over 1000 times that of a brown bear. In addition, the feeding strategies of polar bears are vastly different from their ancestors: Polar bears travel huge distances to exploit energy-rich foods, while Arctic brown bears move little and eke out an existence on an energy-poor diet. There are 19 subpopulations of the species. Polar bears can be found at low densities right up to the North Pole, but their main habitat is the nearshore annual sea ice over the continental shelf, where biological productivity and their main prey are more abundant. The southernmost limit of the bears is in the subarctic waters of James Bay, in Canada, which is at about the same latitude as London, England. For management purposes, polar bears have been divided into 19 different subpopulations based on movement patterns of adult females wearing satellite radio collars. Changing Sea Ice Habitat Changes to sea ice are well documented. The main concern about climate change effects on polar bears is habitat loss and changes to sea ice habitat. The sea ice on which polar bears depend has undergone recent declines in area, duration of cover, and thickness as a result of climate warming. Observed changes to the sea ice and habitat that may affect polar bears are these (Kingsley et al,. 2008): decline in maximum extent of sea ice in winter of about 1.5% per decade loss of multiyear ice (permanent polar pack ice), which is declining about 10% per decade increase in amount of open water shortening of the period of ice cover and lengthening of the open water period increase in the rate of ice drift Changes are happening faster than expected. Studies suggest that the sea ice is changing faster that projected, and there are concerns that the loss of sea ice may have passed a tipping point that could accelerate future declines. Climate projections and sea ice models must be viewed with some caution, but the message is clear: Polar bear habitat is changing. Sea ice affects food sources of polar bears. Climate induced changes to the sea ice may result in changes to the prey species available to polar bears. There are indications that harbour seal (Phoca vitulina) populations are increasing, and that harp seals (Pagophilus groenlandica) are expanding northward. These species are already prey items for some polar bear populations, but if the sea ice continues to change, we may see these species become more important to polar bears as long as the bears have a sea ice platform to hunt from. There is concern that if the ice conditions deteriorate too much, polar bears may be replaced by other top level predators, such as killer whales (Orcinus orca), which are largely excluded from ice covered seas. Climate Change Effects On Polar Bears Some subpopulations are in decline. The evidence for climate change affects on polar bears is not definitive. The definitive effects will come when subpopulations disappear. The status of the various subpopulations of polar bears varies widely: Some are in decline due to climate change effects, and others are not showing any indications of change. The effects of climate change can differ in space and time, but only two or three subpopulations are monitored adequately to be able to confirm long-term trends in abundance and thus provide some insight into what may befall the species over a broader area. The Hudson Bay subpopulation is down by 22%.The most telling impacts of climate change on polar bears have been noted in western Hudson Bay, where declines in their body condition, reproduction, and survival have resulted in a 22% reduction in subpopulation size between 1987 and 2004. Earlier melting of the sea ice in Hudson Bay is the major driving force behind the population decline, but a continuing unsustainable harvest of seals has aggravated the situation. Earlier melting of sea ice has two consequences for polar bears: It shortens the feeding period at a time when recently weaned seal pups are available, and it lengthens the period the bears must fast with less stored fat. While polar bears are well adapted to extended fasts, there is a limit to how long they can survive without food. Females in poor condition give birth to small cubs that weigh less, and lighter cubs have lower survival rates. Over time, low survivorship to adulthood means the subpopulation will decline in number. There are data showing that polar bears in both the southern Beaufort Sea and southern Hudson Bay are also declining in condition, which is often a precursor to subpopulation declines. Polar bears must travel greater distances now. A warming climate is altering sea ice conditions and affecting polar bears in other ways. Sea ice in many areas shifts with wind and water currents, and polar bears often walk against the ice flow to remain in contact with their preferred habitats. Climate warming is reducing ice thickness and extent, which may result in greater ice drift. In effect, the polar bears are on a treadmill, and we are turning up the speed. More energy used for locomotion means there is less energy available for growth and reproduction. Like deforestation in terrestrial habitats, altered sea ice dynamics can increase habitat fragmentation, making movement across the landscape more difficult. Habitat is more fragmented. Some examples of the expected effects of changes in sea ice are the following (Etkin, 1990): increased energetic costs of movement altered home range size and configuration altered subpopulation boundaries reduced access to den areas increased periods without access to prey altered prey species increased time spent swimming, which may chill small cubs and reduce their survival Some bears drowned; others resorted to cannibalism. Other events are more difficult to directly link to climate change but are consistent with predictions. Polar bears observed drowning off the coast of Alaska may have died due to the rapid northward retraction of the sea ice: More open water and greater distances between land and sea ice make it difficult for bears to find refuge. In the same area, killing and cannibalism observed among polar bears may be related to changes in sea ice conditions and lower availability of prey (Heaton, et al, 2006). Adult males appeared desperate enough to prey on other bears. Despite decades of research, such events were never recorded in the past in the Beaufort Sea, but it is consistent with a population under stress. In some areas bears can't get to their food. Changing sea ice conditions are affecting the bears' hunting abilities. In the southern Beaufort Sea, bears were observed in 2005 through 2008 digging through solid ice trying to prey on seal pups. Normally, ringed seal pups are born under snow drifts, which the bears can excavate with relative ease, but clawing through ice up to 70 cm thick is inefficient and possibly an indication of low seal availability. Seals appear to be pupping under sea ice because of altered sea ice conditions and storm events that rafted thinner ice. The long-term consequences for polar bears are unknown, but a reduction in energy intake is likely to affect many aspects of the bear's ecology. Some den areas may be abandoned completely. Recently, a new study in Alaska revealed that polar bear dens on the pack ice declined from 62% between 1985 and 1994 to 37% between 1998 and 2004 (Gagnon and Gough, 2005). This was probably a result of declines in the amount of stable old ice; increases in unconsolidated ice; lengthening of the ice-free period, which reduced the availability and quality of pack ice den habitat; and the long-term protection of denning females, which has resulted in bears with a fidelity to denning on land not being killed by hunters. As the ice continues to change, we can expect some den areas to be abandoned. In some areas, the number of human-bear interactions is increasing. Nutritionally stressed bears that are spending more time on land are approaching settlements or hunting camps seeking food. As the sea ice continues to change and bears become increasingly stressed, further increases in interactions are expected. The future Can polar bears adapt to life on land Will polar bears just adapt to a terrestrial life without the presence of sea ice This notion has been navely proposed by some. Polar bears regularly attain body masses of over 300 kg for females and 500 kg for males. In contrast, brown bears living in the Arctic right next to polar bears rarely exceed 200 kg, reflecting the meager food resources of high latitude terrestrial environments. It is an odd view of evolution that would propose that a highly specialized species with over 200,000 years of evolution could respond in decades or, at best, centuries to the projected loss of their sea ice habitat. Regardless, the niche of a terrestrial Arctic bear is already filled by the brown bear, of which the grizzly is a subspecies. Can we predict the future for polar bears Predicting the future is a precarious venture, but it is clear that the sea ice habitat of polar bears is changing rapidly. Highly specialized species are particularly vulnerable to the effects of habitat loss. In summary, the expected changes in polar bears related to climate warming include these (Comiso, 2002): reduced access to prey species reduced body condition lower cub survival lower reproductive rates lower growth rates increased intraspecific aggression increased cannibalism lower adult survival altered movement rates shifting den areas shifting population boundaries increased bear-human interactions altered prey composition reduction in population size Lose sea ice - lose the species! Loss of sea ice is similar to deforestation of tropical rain forests: lose the habitat and, with few exceptions, you lose the species. Unlike other species, polar bears are unlikely to do well shifting their range further north because the polar basin is deep, cold, and unproductive. Losing the productive coastal habitats would be a serious loss, but the sea ice is more than just a platform, it is the habitat of polar bears and many of the species they rely upon. From phytoplankton to fish, the sea ice is an integral part of the Arctic marine ecosystem. Conclusions Is the sustainable use of biodiversity attractive The reality is that it all depends on the following factors (Amstrup et al 2006): - the location and institutional conditions prevailing. It is not possible to say that sustainable biodiversity use is generally to be preferred to alternative land uses since rates of return will clearly vary according to climate, soil conditions, topography, infrastructure, nearness to market, etc; - but the limited information available does not support the opposite view. Indeed, it suggests that biodiversity use may well be able to compete with the more traditional land uses if there is greater parity. What this means is that sustainable land use competes with alternative land uses if those uses are not subject to privilege and special fiscal treatment, distorted property rights etc. Where such distortions are present - and they are pervasive - biodiversity use may well fail to compete'. Indeed, this is one dominant reason why more investment in biodiversity does not automatically take place; - this problem is compounded by a second distortion - the absence of global markets' in the benefits of biodiversity. In particular, we note that developing countries face major problems of appropriating the global benefits of sustainable use of biodiversity. As long as those global values cannot be captured by host countries, biodiversity will be a risky investment in many contexts. The means of appropriation include resource transfers under conventional aid, transfers under the GEF, debt-for-nature swaps etc. It is imperative that these mechanisms be strengthened and added to. It is also essential that we secure an improved idea of what these global values are in terms of economic quantities; - despite these cautions, the estimates we have drawn together do suggest that there must be many cases where biodiversity investment pays'. Wetlands with the potential for human use, and tropical forests are perhaps the clearest examples, but this conclusion may be influenced by the fact that these systems have been the most studied to date. We suspect that coastal systems would reveal similar high rates of economic return if properly evaluated. References Amstrup, S.C., Stirling, I., Smith, T.S., Perham, C., and Thiemann, G.W. Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea. Polar Biology 29 2006.: 997-1002. Comiso, J.C. A rapidly declining perennial sea ice cover in the Arctic. Geophysical Research Letters 29: 1956, 2002. doi 10.1029/2002GL015650. Etkin, D.A. 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Regehr, E.V., Lunn, N.J., Amstrup, S.C., and Stirling, I. Survival and population size of polar bears in western Hudson Bay in relation to earlier sea ice breakup. Journal of Wildlife Management 2007. 71: 2673-2683. Smith, T.G. Polar bear predation of ringed and bearded seals in the land-fast sea ice habitat. Canadian Journal of Zoology 1980. 58: 2201-2209. Stanley, S.M. Macroevolution, pattern and process. San Francisco: W. H. Freeman and Co. 1979. Stirling, I., Richardson, E. Thiemann, G.W., and Derocher, A.E. Unusual predation attempts of polar bears on ringed seals in the southern Beaufort Sea: Possible significance of changing spring ice conditions 2008. Arctic 61: 14-22. Talbot, S.L., and Shields, G.F. A phylogeny of the bears (Ursidae) inferred from complete sequences of three mitochondrial genes. Molecular Phylogenetics and Evolution 1996a.5: 567-575. Wadhams, P., and Davis, N.R. Further evidence of ice thinning in the Arctic. Geophysical Research Letters 27: 3973-3976. 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