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Executive Summary: This project attempted to link global change in climate and ecosystem change. We specifically looked at the ecosystems concerning bats. Bats are important creatures and it is generally uncommon to find studies done on bats and their role in ecosystems. This paper looked at the increasing global temperature rise as an indicator of how the life of bats have changed in their respective ecosystems. For this, we looked at temperature data gathered worldwide more recently and up to about 150 years ago. We analyzed the data in order to note any temperature and bat population trends that were of relevance to this paper.
Purpose/Problem: Bat populations globally have experienced rapidly declining populations resulting from effects on their environments. Rising average global temperature affect such things as the plants on which certain bats feed and pollinate, along with the insects that other bats feed on. Bats are invaluable players within the biotic component of many ecosystems, and in many instances are very susceptible to drastic temperature increases. Declining bat populations result in food web and plant pollination disruption that have great repercussions in the ecosystems in which they reside. A hypothesis that continues to receive greater support worldwide is that accelerated global warming is occurring due to anthropogenic activities. This accelerated warming is affecting numerous ecosystems and biotic communities because the climate change is exceptionally rapid. Bats, which act as indicator species because of their vulnerability to rapid climate and ecosystem change, are possibly falling victim to global warming because of numerous human activities that release large amounts of pollutants such as CO2 into the atmosphere, affecting world climates.
What We Accomplished: We provided evidence using data that increases in worldwide temperature was something more than a fad or a brief anomaly. Our goal was to provide evidence that supported the hypothesis that increasing temperatures and the resulting climate changes was a trend that is likely to continue at an accelerated rate as long as humans continue to release greenhouse gases that trap heat and increase temperatures. Secondly, we attempted to provide evidence that the resulting climate change affects the insects and the plants on which certain bats feed. Surprisingly, a great amount of research has been conducted involving the study of bat communities. This topic presented a plethora of resources pertaining to the environmental factors affecting bats; with a limited amount including climate change
Relevance: Bats act as another indicator species highlighting the negative effects of rapid global change due to human activities. Bat species act as early warning systems for significant global issues such as global warming and climate change. The bats in and of themselves, because of their uniqueness and amazing evolution as species, deserve protection from human-induced rapid climate change. As mentioned above, bats are invaluable players in their respective ecosystems, controlling insect populations or pollinating numerous plant species as they feed.
How does this topic actually relate to a real-world application?
We were actually trying to show that the effects of global warming have affected even the smallest ecosystems, which can undergo changes that cannot be simulated or predicted using any computer-generated model. The Intergovernmental Panel on Climate Change (IPCC) expects that the average global surface temperature could rise 1-4.5°F (0.6-2.5°C) in the next fifty years, and 2.2-10°F (1.4-5.8°C) in the next century, with significant regional variation. Climate plays a role in maintaining the balance among predators and their prey and the ratios of these "functional groups" of species as natural biological controls over pests and pathogens (infectious disease agents). Freshwater fish, reptiles, birds and bats limit the abundance of mosquitoes, some of which carry malaria, yellow fever, dengue fever and encephalitis. Global warming and increased climate variability can also disrupt biological systems that have evolved over millennia, and which act to control the populations of opportunistic, "nuisance organisms." We specifically looked at the case of bats and the real or potential effect of global warming on their ecosystem.
It was generally believed that bat populations have declined worldwide in recent decades. Because bats have low reproductive rates, populations are very susceptible to elevated mortality. There was developing concern that many species of bats were increasingly affected by multiple actions of humans. Bats faced multiple threats of ignorance, suspicion, pesticide poisoning, roost destruction and closure, habitat loss, over-exploitation, and extermination as pests. Among mammals, bats are the second most diverse order (after rodents) and occur on all continents except Antarctica. Bats often range widely in their foraging activities and habitat modifications such as urbanization, agriculture, and other land use practices may affect local plant and insect populations and thus the food resources of bats. At present, however, virtually nothing is known of the specific effects of global warming on bats although certain predictions can be made based on the biology of bats.
Fig 1. Rising temperatures across the planet in each hemisphere and their total rise across the whole planet
One of the most important functions of bats in plant ecology is in plant pollination. Typically, bats help in disseminating the pollen of flowers. This is also evident in their inadvertent aid to maintain a balance of insect populations on earth. Most species of bats appeared to be specialized in pursuing and capturing selected kinds of insects. It is commonly known that about 75% of bat species rely on insects for sustenance. Furthermore, bats are dependent upon a reliable and consistent "supply" of prey, even though specific insect populations grow and disappear over the course of a summer season. Changes in worldwide insect population occurrence or distribution would be expected to affect numbers and species diversity of bats. Thus, the scope of this project was to actually show that bat populations have declined in general due to rapid climate change, and their effects are noticeable.
Background: We found an abundance of interesting information about bats while going through numerous web sites. While the tidbits pertain to most of the bats, some of them may specifically be aimed at one particular species of bat. Hopefully we can expound upon widely held beliefs regarding bats. Most of the species of bats do have good eyesight, but, especially pertaining to the species that eat bugs, rely heavily on a radar-like capability, known as "echolocation", to navigate and catch prey (Reference No.17 see link). While bats species more often rely on bugs for sustenance, a significant number of bats species have developed an acute sense of smell, which helps them find the fruits that they prefer. Bats are also invaluable in terms of the other ecosystem functions they perform along the lines of "seed dispersal" and "pollination (Reference No.17 see links)." As with numerous bee species, bats inadvertently pollinate as a positive fringe benefit during their normal feeding habits.
Please click on the link Bats to learn about the tremendous attributes that numerous bat species exhibit along with the functions they perform. Considering bats are either "hibernators or migratory" mammals, it is evident that rapidly increasing temperatures would have adverse affects on these populations (Reference No.17 see links). As people understand the highly evolved nature of these mammals, previous, widely held beliefs pertaining to bats no longer seem practical or fair. While it was easy to characterize bats as being rabid nocturnal predators, the more insight we gain into the individual bat species and their respective communities, it becomes easier to put aside the myths. Once people are able to allow a greater appreciation of the most abundant and one of the most under appreciated mammals in existence, we should be able to actively address the stresses being placed on bat populations.
Bats are an excellent indicator species because on their species diversity and great dispersion throughout the world ecosystems. As we see their populations diminishing with each new study, we should truly condemn the negative effects that the activities of man, even in this case global warming, has on ecosystem stability and integrity along with biodiversity. Hopefully, the more knowledge that people gain regarding bats, there will be great collective human interest in the protection of the bats for the sake of the bats alone. Often, species or habitat protection requires some particular value to be placed on it before it is worthy of protection from substantial human interference. While the aim of this paper was to present information that supported claims that bat communities were at risk due to human activities, great benefit will be derived if this paper actually provided sufficient information that promoted bats in a light that accents their unique qualities. Bats species warrant all reasonable protections solely because of their long, amazing evolution into highly developed mammals. The protection of these indicator species will act as a shield for the biota they interact with along with the ecosystems in which they reside.
CO2 – Temperature link:
The development of countries of the world has led to increased usage of fossil fuels for automobiles. Due to the increased burning, CO2 has been released into the atmosphere in increased amounts. The amount of CO2 has caused a tremendous alteration in the cycles that occur naturally in the ecosystems of the earth. Human activities have altered the composition of the atmosphere of the earth so much that the earth is notable to assimilate the huge amounts of CO2 released into the atmosphere at one go. There has been a significant buildup of greenhouse gases in the atmosphere that carbon dioxide has actually been a heat-trapping gas thus increasing the temperature of the earth.
The Temperature and CO2 Relationship:
The temperature of the earth has been optimal for living beings to exist. The heating of the earth has been a natural process for millions of years where the sun heats up the earth and earth reflects some of the sunlight. The already existing CO2 has been instrumental in keeping those small amounts of heat and ensuring that life continued to exist on earth. Problems occur if the amount of CO2 in the atmosphere begins to increase due to increased emissions from combustion of fossil fuels and other human activities. The greenhouse gases can actually trap these molecules from the sun and cause them to reflect from the surface to the atmosphere and come back to the surface. In this way, the molecules are prevented from escaping and so the temperature of the earth increases. There has so far been no accurate way of determining the exact temperature increase but it is widely believed that the temperature of the earth will increase by 1- 4.5 ° F in the next fifty years (visit www.epa.gov/globalwarming for more details).
Figure 1a: The above graph tracks the temperature increase over the past 120 years from 1880 until 2000.
The IPCC has developed different scenarios about the change in emissions of greenhouse gases over the coming century. They make different assumptions about population growth, and changes in energy use and economic growth, but all are based on the assumption that the world carries on with 'business as usual', which is failing to intervene to curb climate change. These scenarios give annual emissions of CO2 ranging from current levels to six times current levels called the IS 92a-f scenarios. (available at http://panda.org/resources/publications/climate/climate_change/page3-4.htm)
The Unknown Parameters:
Scientists have identified that our health,
agriculture, water resources, forests, wildlife and coastal areas are vulnerable
to the changes that global warming may bring. But projecting what the exact
impacts will be over the 21st century seems to be very difficult. This has
become the norm if a local region is to be considered. A local region seems to
be more difficult to predict as compared to a global region.
At this point, the questions that arise are
· How long is the warming going to continue?
· What are the adverse and beneficial effects of this?
Currently, we are
unable to answer all questions regarding global warming. However, it has been
universally accepted that increased CO2 emissions due to human
activities have contributed to increased temperature around the world.
The following image has been taken from http://www.ipcc.ch/pub/tar/wg1/035.htm and shows the projected increase in temperature due to an increase in CO2 concentrations around the world. Note that the graph gives a projected rise in temperature due to an increase in concentration of CO2. If the concentrations of CO2 were to rise exponentially in the next three hundred years, then the temperature of the world would increase by 2 º C from the present levels.
We placed a call to Jackie Bellwood of the Cincinnati Nature Center on April 11, 2002. Jackie was referred to us because she has a great deal of interest in bats and has done quite a bit of research on many species. The conversation was fruitful for a number of reasons. She provided us with a great deal of background information of bats pertaining to their biology, feeding habits, and roosting requirements. One of the most beneficial aspects of the conversation derived from hibernation and cave dwelling habits and requirements for many bat species.
While not all bat species live or even hibernate in caves, many rely on caves for shelter. A number of factors affect bats and more specifically, their decision on where to hibernate when the time comes. Some bat species do live in caves year-round, but others only use the caves for hibernation. One important factor that plays into the roosting and hibernate requirements of bats is that they are creatures of habitat. Bats are accustomed to returning to and relying on the same cave year after year for hibernation. Ms. Bellwood informed us that the internal temperature of caves normally do not fluctuate more or less than 1 ° F annually. What was amazing was the fact that the relatively constant year-round temperature within the cave was the average of the year-round above ground temperatures. In North America, for example, year-round temperatures usually fluctuate greatly as the four seasons cycle.
Bats in New Hampshire return to the same caves every year for hibernation. The bats are accustomed to inner cave temperatures that remain constant around 40 ° F. Roost requirements are very important at this point. A bats ability to fly possibly makes it appear that it has an ability to relocate to a new cave if it is needed. Unfortunately, caves appropriate for use at a bat dwelling are not the most bountiful natural habitat in North America. The numbers of caves are limited and bats would likely need to travel great distances in order to locate a new site. Additionally, realizing that bat colonies populations often are millions strong, roost requirements must provide for huge colonies.
The lack of data or science journal articles correlating increasing global temperatures and decreasing bat populations also encouraged us to contact bat organizations via e-mail to gather more information. One of the organizations that responded was The Bat Conservation Trust of the United Kingdom. Amy Dunkley was kind enough to respond, and told us that the organization not aware of any significant current threat to bat populations in the UK due to global warming. Specifically, she stated, "there are no direct links between global warming and bat population decline." She concurred with others that there are currently much more direct human threats present that are damaging bat populations.
Decrease in Animal Populations:
One of the most important reasons for the decrease in our “winged friend” populations is their migration to different areas around the globe. It has been estimated that the populations of endangered species and those that live in polar regions are at perennial risk from increased concentrations of carbon dioxide. A report at http://www.commondreams.org/headlines/090100-02.htm predicts that global warming could alter more than a third of the existing habitat in the states of Maine, New Hampshire, Oregon, Colorado, Wyoming, Utah, Idaho, Arizona, Kansas and Texas. It also says that in the following century, some species would have to migrate up to 10 times faster than after the last Ice Age. Certain species will need to move or migrate northward at a rate which they have not experienced previously. This means that many species will not be able to migrate as fast as those that can adapt to the new environment.
Reference to Bat Populations:
Before the 1970's, the population status of Indiana bats was poorly understood because the locations of many of their winter hibernacula were unknown, and the counts that were conducted were made irregularly and inconsistently. Since 1983, there has been a new census where the bat population has significantly decreased to 347,890 in 1993. Although the national trend indicates a 22% decline during the past 10 years, this decrease has not been consistent across the species' winter range. The decrease in bat population was evident in Missouri where the population has gone down significantly. However, bat populations in Indiana have increased over the years and have stabilized in Kentucky.
What is happening then?
In Northern Minnesota, it has been discovered that winters have been unusually warm. The temperature has increased by 3.5° F over the last century. It has also been discovered that the temperatures inside caves in New Hampshire have increased over 1° F. A small increase in the temperature can actually be unfavorable to bats as it affects their hibernation, feeding and migratory patterns.
Humans have also been responsible for decline in bat populations. Human activity causes bats to wake from hibernation and use their reserve of fat.
· Human vandalism seems to be the most important cause for population decline. It has been estimated that 10,000 Indiana bats were killed in a cave located in a Kentucky state park by three juveniles, who tore masses of bats from the ceiling and trampled and stoned them to death.
· Continued disturbance of roosting sites may cause bats to abandon a particular roost altogether. While some may be successful in finding homes in buildings, others may become homeless and be unable to survive because of the loss of roosting sites.
· Fear and ignorance also plays a big part in their habitat destruction. Bats have always been associated with horror stories and it has actually persuaded people to kill them instantly rather than examine them.
· Deforestation of areas has detrimental effects on bat populations. This makes them easy prey for predators.
· Human consumption of bats has already caused extermination of some species
· Severe winters have caused bats to freeze to their deaths. Those that are near the entrance of the caves are more susceptible to cold temperatures.
Records indicate that the population of Mexican free-tailed bats had decreased by 99.9% within a span of six years in the early 1960’s. In the United States, it is estimated that nearly 40% of the 44 bat species are endangered or threatened. In Latin America, the rise in population of vampire bats contributed to the indiscriminate killing of all bat species by poorly trained government agencies and local farmers who were unaware that the majority of the other 270 species were highly beneficial.
Global warming affects on different species:
The ability to locate parallel or similar examples of climate change affects of non-bat populations helped substantiate the claim that increasing average temperatures affect ecosystems or specific species. Camille Parmesan headed up a scientific study in Europe. Her object of the study was 35 species of butterfly in Europe. She and many colleagues visited a number of European butterfly researchers during the study to take note of any particular trends within the 35 species. Mari Jensen of ABC News documented the findings of the study in her article, Butterflies Shifting North: Global Warming Sends Some Packing (http://butterflywebsite.com/Articles/ShowArticle.cfm?ID=410).
The most significant finding pertaining to global warming and its affects on species was that greater than 60% of the 35 butterfly species studied were now living up to 150 miles further North of what previous records indicated. These changes occurred within the last 100 years. These northern migrations concurred with the temperature data indicating increasing average global temperatures over the last 100 – 120 years. From the findings in this article, a cause and affect relationship appeared to exist between increasing average temperatures, climate change, and northern movement of many of the butterfly species.
The findings in this study, which documented the affects of global warming on these significant indicator species appeared to substantiate a claim that global warming affects species and subsequently ecosystems. As the value of each species comprising the biota of all ecosystems is further appreciated, the affects of more northerly movement of individual species one at a time will be noticed. As the relationship between increasing CO2 levels and rising average temperatures continues to be proven, and the effects on populations on more than 20 species affected according to the butterfly study noted above, the biota communities within ecosystems will change more rapidly. While it is difficult to predict which species will initially be affected more, as the predicted increases in average temperatures are realized in the 21st Century, climate effects on what may be more resilient species at the current time, will begin to affect those more resilient species.
A 1 ° F increase in temperature over approximately the last 100+ years appeared to have affected certain butterfly species. The projected 1 – 4.5° F increase (www.solcomhouse.com) over the next 50 years in average global temperature is likely to have a tremendous affect on species, possibly including bats, due to their sensitivity to temperature change. The cumulative affects of currently shifting or declining species populations such as numerous butterfly species on their affected ecosystems compounded with direct affects of continued global warming on new species should produce much more dynamic change to individual species and ecosystems.
Our hypothesis was partially supported. As all of the accumulated and analyzed data appeared to indicate, that certain aspects of our hypothesis were supported while support for the heart of our hypothesis, that there was currently a direct relationship between declining bat populations and global warming, was not supported. The aspects of the hypothesis that were supported included the belief that average global temperatures were gradually increasing and that many bat populations, specifically in North America, were in decline.
We were able to include graphs that presented the temperature data for about the last 100 years that indicated a steady increase in temperatures worldwide that amounted to approximately an increase of over 1° F. We were unable to locate any temperature data that either indicated a reverse trend showing decreasing average global temperatures or stable, non-dynamic temperatures over the same period of time. The compiled data of increasing concentrations of CO2 in the atmosphere increasing since the beginning of the Industrial Revolution indicated there was a relationship between the increasing CO2 levels and increasing average global temperatures.
We accomplished part of our hypothesis by providing data that clearly indicated that huge human disturbances were affecting bat populations. Individual colonies along with entire species, such as the Indiana Bat, were clearly in decline recently. However, the temperature increases over the past 120 - 150 years pales in comparison to the dramatic, immediate effects of other anthropogenic damage. Direct damage to bats and their ecosystems through roost destruction, pesticide use, outright killing, and other man-induced damage other than accelerated global warming appeared to be the primary contributors to rapid declines in the bat populations we studied. As noted earlier, all of the professionals we contacted, who were studying bats, had access to bat data and were knowledgeable to current threats to bat communities, believed that the current significant threats to bats were anthropogenic, but separate of global warming.
While forecasting the future is always difficult, one thing that out data appeared to indicate and that some of the professionals we contacted also lend support to, was the likelihood that global warming will play a huge role in ecosystem change later in the 21st Century. Bats, as has been indicated in this paper, are very susceptible to temperature increases and also to anything that affects the dynamics and food web in their ecosystems. It was difficult to predict what plant, animal or insect species would first be affected by increasing average temperatures, or when exactly they would be affected, but the predicted increases in CO2 concentrations and concurrently average temperature would force certain species into more rapid migrations, open the door to invasive species, or cause extinctions. It is apparent that a 2 - 10° F increase in average global temperatures as has been predicted by various models will surpass temperature and CO2 increases spanning thousands of years inevitable altering numerous ecosystems as they currently exist because the climate change will be so rapid.
Another video of bats: Click here to see it (Quick Time plugin is needed)
1. Bats Magazine. BCI Research Scholars, Making a Difference for Bat Conservation Geiselman & Acker, vol 19, no 3, Fall 2001. Magazine article discusses the human threats posed to bats worldwide. Magazine itself is a good resource.
2. Book: Effects of past global change on life / Board on Earth Sciences and Resources, Commission on Geosciences, Environment, and Resources, National Research Council - Washington, D.C.: National Academy Press, 1995 Read Tropical Climate Stability and Implications for the Distribution of Life by Eric Barron This book discusses historical effects and responses of ecosystems and biodiversity due to climate change.
3. Biotic response to global change: the last 145 million years / edited by Stephen J. Culver and Peter F. Rawson - New York: Cambridge University Press, 2000 This is another historical study regarding the effects of global climate change on biota.
4. Earth system responses to global change: contrasts between North and South America / edited by Harold A. Mooney, Eduardo R. Fuentes, Barbara I. Kronberg - San Diego : Academic Press, c1993 Text includes regional and hemispheric effects of global climate change.
5. Atlas of satellite observations related to global change / R.J. Gurney, J.L. Foster, C.L. Parkinson - Cambridge [England]; New York : Cambridge University Press, 1993 Visual aids in studying various environmental and meteorological factors pertaining to global climate change.
6. Carbon charges as a response to global warming: the effects of taxing fossil fuels - Washington, D.C. : Congress of the U.S., Congressional Budget Office,  Discusses regulations calling for carbon charges to industry in order to combat climate change.
7. Global climate change and human impacts on forest ecosystems: postglacial development, present situation, and future trends in Central Europe / J. Puhe and B. Ulrich ; chapter 8 by A. Dohrenbusch - Berlin ; New York : Springer, c2001 Highlights past, present and potential future human induced climate change effects on forests
8. www.esd.ornl.gov/research/egcs.html - Research about studying, understanding and prediction of ecosystem change and response to climate change.
9. www.globalchange.gov - US global change research program providing articles, links, and satellite images pertaining emissions and rising temperatures due to human activity.
10. www.climateark.org - Good resource that addresses climate change and possible solutions to negative human activities through the expanded use of things such as renewable.
11. www.gcrio.org/online.html - Site contains links to numerous documents regarding US positions, responses, etc. to climate change issues.
12. http://www.npca.org/wildlife_protection/wildlife_facts/bats/default.asp - This is a great site that offers good description of what bats are, how abundant and valuable a mammal they are, and specifically how human activities threaten them.
13. http://geochange.er.usgs.gov/sw/impacts/biology/bats/ - This site discusses the many hazards man poses to bats, including the rise in global temperatures due to our activities.
14. http://www.batcon.org - A bat-friendly site. This site praises bats, giving good descriptions as to their gentle and beneficial nature. Provides many bat-links to read up on bats in different regions.
15. http://dailynews.yahoo.com/h/azstar/20020207/lo/_big_room_to_open_1.html - Article highlights climate change observations pertaining to the effects on bats in Arizona. It has been apparent that bat caves have been drying in response to drought brought on by climate change.
16. http://www.epa.gov/globalwarming/ - February 15, 2002 EPA's Global Warming website. Interesting to see how federal agency defines and characterizes global warming.
17. http://www.cccoe.k12.ca.us/bats/conserve.html - Good resource explaining bat's habits, characteristics, and their value to humans and the rest of the environment.
18. www.solcomhouse.com/globalwarming.htm - Site containing information on IPCC and other information related to climate change, policies etc…
19. http://biology.usgs.gov/s+t/frame/c164.htm - Site giving information about declining populations of Indiana Bats in North America.
20. http://www.desertusa.com/jan97/du_bats.html - Good bat data relating to range, biology and vital statistics
21. www.batworld.com - Non-profit organization focusing on bat education, rehabilitation and bat adoptions
22. www.cws-sct.ec.gc.ca/hww-fap/bats/bats.html - Map distribution of the little brown bat
23. www.wildlife.state.nh.us/brownbat_facts.htm - Information about Brown Bats
24. http://endangered.fws.gov/bats/threats.htm - US Forest & Wildlife Service Information on U.S. Bat species ( gives reasons for bat population decline)
25. http://www.forestwatch.org/iBat.php3 - Information and correlation about Indiana Bats and global warming
26. www.bats.org.uk - Talks about English Bats
- Gives statistics about declining bat populations in the U.S.
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