Ecosystems

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5.1.2.b

Ecosystems are subject to many pressures. You can probably name several. Land-use changes, pollutants, grazing by livestock, introduction of exotic species, and natural climate variability, all affect ecosystems.

In many parts of the world, scientists have observed changes in ecosystems that are consistent across a wide variety of localities. These changes are just what you would expect as a result of regional temperature change. ‘The probability that the observed changes in the expected direction could occur by chance alone, is negligible.’ Climate Change 2001 Synthesis Report, p 54

Figure 1 below, shows the locations at which studies have documented regional temperature change impacts. The consistency in these observed changes across regions, heightens the confidence that changes in the biological systems is a result of the changes in regional climate.

There is high confidence that 20th century climate changes have had a discernible impact on many biological systems. What’s more, these systems are sensitive to climatic changes that are small, relative to changes that have been projected for the 21st century.

Changes have been seen in species distributions, population sizes, and the timing of reproduction or migration events. For example, some animal ranges are moving toward the poles, i.e. north in the northern hemisphere and south in the southern hemisphere. Some animals are moving to higher elevations. There are changes in body size. Animal breeding, plant flowering and insect emergence are all happening earlier in the spring. Regional climate change appears to be a major contributing factor. (IPCC WGII section 5.4.3)

Disturbances such as fires, droughts, and blowdowns have changed in intensity, and frequency. These events are affected by regional climatic change and land-use practices. These events then affect the productivity of species, and the species composition within an ecosystem, particularly at high latitudes and high altitudes.

Frequency of pest and disease outbreaks have also changed, especially in forested systems, and can be linked to changes in climate.

Figure 1. Locations of long-term studies which show regional climate change impacts on biological systems.

Locations at which systematic long-term studies meet stringent criteria documenting recent temperature-related regional climate change impacts on physical and biological systems. Hydrology, glacial retreat, and sea-ice data represent decadal to century trends. Terrestrial and marine ecosystem data represent trends of at least 2 decades. Remote-sensing studies cover large areas. Data are for single or multiple impacts that are consistent with known mechanisms of physical/biological system responses to observed regional temperature-related changes. For reported impacts spanning large areas, a representative location on the map was selected.

Source: Climate Change 2001 Synthesis Report p. 285

Many threatened systems are at risk from climate change because they face pressures from human activities such as land-use and pollution. Critically endangered species are generally species with small ranges, low population densities, restricted habitat requirements, and species with suitable habitat distributed.

CHART NEEDED—6 Columns, 7 Rows–plus two extra

Source: Climate Change 2001 WG II, section 5.4.3

Table 2: Species found in studies to be associated with regional temperature change.Source: Climate Change 2001 WG II, section 5.4.3
Table 2: Species found in studies to be associated with regional temperature change.a

CHART NEEDED — look back to cd

aThe columns represent the number of species in each region that were found in each particular study to be associated with regional temperature change. For inclusion in the table, each study needed to show that the species was changing over time and that the regional temperature was changing over time; most studies also found a significant association between how the temperature and species were changing. The first number indicates the number of species changing in the manner predicted with global warming. The second number is the number of species changing in a manner opposite to that predicted with a warming planet. Empty cells indicate that no studies were found for this region and category.

Source: Climate Change 2001 Synthesis Report p. 286

Activity:
1. What do you think is the difference between critically endangered, endangered and vulnerable species?
2. Are critically endangered, endangered or vulnerable species more susceptible to climate change? Why?
3. Create a bar graph using the Table 1 data, for critically endangered species of each type for each region.
4. Is there a class of vertebrate species which is has the most species represented across all regions?
5. Is there a region that has more critically endangered species than others?
6. Look at Table 2. What kinds of species have been added compared to Table 1?
7. What is the difference between the 2 numbers for each type of species?
8. Look at the numbers of species changing in the manner opposite to what you would expect with a warming planet. What are some possible explanations for this?
9. What areas have had the most studies? See table 2 and Figure 1. Why do you think this is the case?

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