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Exercise #3: Polar Bears and Climate Change?

Learning Objectives


In this exercise, you will learn how animals are affected by climate change. This exercise specifically deals with polar bears and climate change, but could easily be applied to any other species, including animals, plants, protozoa, bacteria, fungi, or viruses. First you will research the life history of polar bears to become more familiar with the species and the environmental requirements of the species. Next you will use GCM predictions to discuss how the environment might change in the near future (50-100 years). You will then discuss what kinds of affects climate change could have on polar bears, including direct effects (how climate change affects the physiology of the species) and indirect effects (how climate change affects the habitat and food sources of the species). Lastly, based on what you have learned about polar bears and climate change, you will analyze what you think will happen to polar bears as the climate changes, and discuss whether humans should make efforts to conserve the species.


Bloom, Arnold J (2010) Global Climate Change, Convergence of Disciplines, Sinauer Assoc., Sunderland, MA.

IUCN Red List at http://www.iucnredlist.org/.

IPCC (2007). Summary for Policymakers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 7-22.

Audobon Report: Niven D, Butcher G, Bancroft G, Monahan W, Langham G (2009) Birds and Climate Change: Ecological Disruption in Motion. A Briefing for Policymakers and Concerned Citizens (Audubon Society, New York).

Lü, Z., Wang, D. & Garshelis, D.L. (IUCN SSC Bear Specialist Group) 2008. Ailuropoda melanoleuca. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. . Downloaded on 25 September 2012.

Parmesan, C. & Matthews, J. 2006. Biological impacts of climate change. In: Principles of Conservation Biology, Third Edition. M.J. Groom, G.K. Meffe, & C.R. Carroll (eds.) Sinauer Assoc., Sunderland, MA.


Background: How are species influenced by climate?

How does climate influence you? You might wear a jacket on a cold day, or shorts on a warm day. You can pick blackberries to eat during the summer and apples during the fall. You can snow board during the winter and water ski during the summer. All of these activities are influenced by climate, primarily temperature and precipitation. As an omnivore, the food you eat is also influenced by climate because plants have different growing seasons. As part of the human race, you are able to adjust to changes in climate. You can turn on your air conditioner if it is hot and get water from your faucet when there is a drought. During heavy rains, you can depend on the infrastructure of your city to prevent flooding (hopefully). If local crops are killed by an unseasonable frost, you can buy fruits and vegetables that have been shipped from around the world.

All species are affected by climate. Luckily, humans are able to quickly adapt to a changing environment through behavioral modifications. Most other species, however, are not able to adapt so quickly. This has been demonstrated many times during Earth’s history when a changing climate led to mass extinctions.The IPCC predicts that 20% to 30% of all species on Earth will face extinction during this century (IPCC 2007).

In this exercise, you will learn about how climate affects polar bears. You will research the habitat requirement of polar bears, how climate is predicted to change in the next century, and infer how climate change might affect polar bears. As you go through this exercise, keep in mind that this process can be applied to any species, be it animal, plant, bacteria, or virus.

Habitat Requirements of Polar Bears

There are MANY resources you can use to learn about polar bears (or any species), on the internet, in academic journals, and books. One very good resource is the International Union for Conservation of Nature (IUCN). The IUCN is a global environmental organization that has created the Red List which evaluates the conservation status of species on a global scale, highlighting species threatened with extinction.

Visit the IUCN Red List at http://www.iucnredlist.org/ and search for polar bear. Click on the “Full Account” tab for the most information.

Describe polar bears

1. Where do polar bears live?
2. What is the population size?
3. Describe the status of the species, is it considered endangered?
4. What kind of habitat/environment does it live in?
5. At what age, how, and where does it breed? Is the reproductive potential high or low?
6. What do they eat?
7. What are its predators?
8. What are the four main threats to the species?

Describe the population

1. How has species abundance changed over time?
2. How has the species range changed over time?

Describe climate change predictions

What do Global Climate Models (GCMs) predict will happen to climate in the area where polar bears live? Read Chapter 4 of your text book, paying special attention to the section Future World. This section describes predictions that GCMs make for temperature, sea level, quantity of precipitation, ocean pH, intensity of major storms, and frequency and severity of forest fires.

Discuss how the habitat might change

1. How will changes in the physical environment (such as temperature, precipitation, salinity, etc) DIRECTLY affect the species? For example, will an increase in temperature change the physiology of polar bears? Will they start overheating?

2. How will changes in the habitat INDIRECTLY affect the species?


Climate change is not a new phenomenon. In Earth’s history there have been many ice ages followed by warming periods. Although some species went extinct during these periods of climate change, many species survived by acclimating (like plants do under increased CO2) or adapting, either genetically or behaviorally, to their changing environment. The reason current climate change is a major concern for plants and animals is because the climate is changing much more rapidly than it has in the past. Adaptations take time to spread through populations. While some species are capable of rapid adaptation and will likely survive the current climate change, species with long generation periods, already restricted habitats, or habitats that are impacted by humans are in greater danger.

Genetic Adaptation

Genetic adaptation takes place in individuals and spread through populations over generations. The longer the life span of the individual, the longer adaptation takes to spread through a population. Usually, an adaptation consists of a genetic mutation in an individual which gives that individual a better chance at surviving and reproducing. Imagine a species of moths that are bright green. These moths live in tree canopies, where their green coloration hides them from predators. Yet green is a problem if the moth ventures out of the canopy onto the trunk of the tree. The moth is then conspicuous and is more likely to be found and eaten by a predator. Imagine one individual that has a mutation in a gene that codes for coloration. Instead of being bright green, this moth is brown. The brown moth can live in the canopy where it blends in with leaf shadows, and it can live below the canopy where it blends in very well with tree trunks. The brown individual is able to hide from predators better than the green moths and is therefore more likely to survive and reproduce than green moths. The brown moth passes on its adaptive mutation to its offspring, who in turn survive and reproduce more than their green counterparts. In this way, the brown mutation spreads through the population. The brown mutation is called an adaptation because gives individuals a better chance of surviving to reproduce.

Behavioral Adaptation

Species can change their behavior to suit a new environment. As climate changes, animals can move to places where the better suits them. Some birds do this on a yearly basis — they migrate to the arctic to breed during the summer and spring, but when temperatures become inhospitable during the winter, the birds fly south to warmer climates.

As high altitude or latitude regions warm, the growing season is expanded and species that were once unable to live in those regions are now able to expand their range poleward or to higher altitudes. A poleward shift in distribution has been observed in many species. In 2009, the Audubon Society reported that 58% of the 305 bird species that winter in North America have shifted their ranges northward by an average of 35 miles (Niven et al. 2009). The study found the same trend in nearly every type of bird species studied including land birds, water birds and coastal species.

Not all species can move into more suitable areas. For example, alpine species are specially adapted to live in high mountain habitats. As higher altitudes warm, alpine species will have to move farther up the mountain to maintain living in their alpine habitat. But they can only move so far, eventually they will reach the top of the mountain.

Some species are unable to shift their ranges to follow habitat changes because they are impacted by human activity. For example, the giant panda is confined to south-central China. Bamboo makes up 99% of their diet, thus pandas are limited to habitats with dense bamboo forests. The fossil records indicates that giant pandas used to range throughout most of southern and eastern China (Lü et al. 2008). However, human development and cultivation of lower habitats has restricted their range to portions of six isolated mountain ranges. Because pandas are constrained by humans, they will not be able to alter their range in response to climate change.

Shifting species ranges also means competition will arise between species. One dramatic example of this has been observed between the red fox and the arctic fox (Alopex lagopus). The arctic fox is well adapted to the cold environment in which it lives. It has long thick fur, small ears, and short legs, all of which help it retain warmth. In comparison, the red fox has a larger body size which means a larger surface area and in turn more heat exchanged with the environment. The red fox has long ears, long legs, and for these reasons is not well suited for cold environments. But as polar regions warm, locations that were once occupied by the arctic fox are now becoming suitable habitat for the red fox. Over the past 70 years, across northern Canada the red fox has expanded its range northward while the Arctic fox has contracted (Parmesan & Matthews 2006). Red foxes and Arctic foxes are now in competition for resources like food and shelter because their ranges have started to overlap.

What do you think will happen to polar bears?

1. Based on your answers above, do you think polar bears are threatened by climate change?
2. Do you think polar bears will be able to adapt to climate change? Why or why not?
3. Do you think humans should make an effort to conserve polar bears? If no, explain why not. If yes, describe what we can do.

Now that you have completed this exercise, your essay assignment will be to choose a different species and report on how climate change will affect that species.