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Answers to the exploration questions: global threats to biodiversity

If you are wondering where the suggested answers came from, you can review the videos and articles in this tutorial.
1.     After watching the climate change video in this tutorial, your friend says to you “Hmm…in terms of global change, I always thought that the biggest threat to biodiversity was the amount of carbon dioxide (CO2) that humans were adding to the atmosphere. But now I think that the biggest issue is the faster rate of CO2 addition rather than the amount.” What do you think? Is the biggest climate change threat to biodiversity the amount of CO2 humans are adding to the atmosphere, the faster rate, or both?
Answer: A complete answer would mention that both the amount of CO2 that humans are adding to the atmosphere and the rate at which they are doing so are big threats to biodiversity. There have been periods of time in Earth’s history when CO2 levels were at or near our current atmospheric concentrations, and we know from the fossil record that those times had mass extinctions and a global loss of biodiversity. Based on this evidence, scientists predict similar outcomes from the current high levels of CO2. What is unique, and even more troubling, about our current state of global change is that never before in Earth’s history have CO2 levels risen so quickly over such a short period of time. The rate at which CO2 is being added to the atmosphere is the highest ever known to have occurred in Earth’s history. Populations of many organisms will not and do not have enough time or the ability to move to new environments or adapt to high concentrations of CO2.
Graph from video: How does climate change affect biodiversity?
The graph above shows the ups and downs of CO2 concentration in Earth’s atmosphere over thousands of years. What you should notice is that the periods of time in Earth’s history that had higher concentrations of CO2 happened over the course of hundreds of thousands of years. Since the Industrial Revolution, humans have increased atmospheric CO2 by 30-35%. Ice core records show that our current CO2 concentrations are unmatched in the last 650,000 years. In short, it is both the amount of CO2 humans are adding to the atmosphere as well as the rate at which we are adding it that are global change’s biggest threat to biodiversity.
2.   You overhear your brother explaining to his girl friend that ocean acidification is a major threat to biodiversity and that the cause of ocean acidification is acid rain and chemical pollutants that are dumped into the oceans. Do you agree or disagree with your brother’s explanation of ocean acidification? In a few sentences, explain why or why not. HINT: You can check out the demystifying ocean acidification and biodiversity impacts video for more information on pH, ocean acidification, acid rain, and chemical pollutants.
Answer: A complete answer would mention that although acid rain and chemical pollutants that are dumped or washed into the ocean can change the pH of the water for a brief amount of time in the immediate area, those localized effects are quickly diluted by the rest of the ocean water; acid rain and chemical pollutants are not the cause of the global phenomenon of ocean acidification. Scientists use the term ocean acidification to refer to the decrease in pH of Earth’s oceans as the oceans absorb atmospheric carbon dioxide (CO2). As the concentration of CO2 increases in the atmosphere, more CO2 is absorbed by the oceans. Once it is dissolved in the ocean water, the CO2 undergoes a series of chemical reactions that release hydrogen ions that cause a decrease in pH.  The lower the pH of a liquid, the more acidic it is. Since the Industrial Revolution, the ocean’s pH has decreased from an average of about 8.25 to about 8.14. But remember, the pH scale is logarithmic, so each step is a factor of 10. The decrease in pH from 8.25 to 8.14 is actually an increase in acidity in the ocean of about 30%!
Your brother is correct that ocean acidification is a major threat to biodiversity. As you might remember from the tutorial on global distributions of biodiversity, each species has a set of environmental conditions or tolerance ranges to which it is adapted. These adaptations determine where the species can live. Factors such as temperature, humidity, and pH are some of the most important environmental factors that determine species distributions. As ocean acidification decreases the pH of the world’s largest environment, we can expect that many species' tolerance ranges will be exceeded and that there will be an overall loss of biodiversity.
3.     In a few sentences, describe some of the impacts that global change in temperature is expected to have on biodiversity.
Answer: A complete answer would mention that biodiversity is impacted in many ways as the result of the global temperature change (commonly referred to as global warming) that Earth is now experiencing. Global warming is the result of increased concentrations of greenhouse gases, such as carbon dioxide (CO2), in our atmosphere. The Intergovernmental Panel on Climate Change estimates that the average global temperature is going to rise .01 to 2.9 degrees Celsius (2 to 5.2 degrees Fahrenheit) by the end of this century. An increased average global temperature will have many impacts. Ice that covers polar continents, such as Antarctica or Greenland, will melt, causing sea level to rise by about 4 to 6 meters (13 to 20 feet) as the melted continental ice flows into the ocean. Low-lying land next to the oceans will be flooded and habitat will be lost for humans and other organisms. This will force species’ ranges to shrink, shift, or be lost completely, decreasing population sizes and driving some to extinction. Increasing temperatures will also change the ranges of both warm and cold-adapted species. Warm-adapted species will be able to extend their ranges into higher latitudes and altitudes, while cold-adapted species will see a shrinking of their ranges as they are forced into higher latitudes and altitudes until there is no place left to go.

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