Unit 3b. Earth’s Changing Biomes



Figure 3.b.1




A biome is defined as, "a major regional or global biotic community, such as a grassland or desert, characterized chiefly by the dominant forms of plant life and the prevailing climate." There are a wide variety of biomes, including tundra, tropical and temperate rainforest, taiga or boreal forest, temperate forest, grassland, shrubland, savanna, and desert to name a few. Biomes are generally created by the interplay of temperature and precipitation in a given region on the Earth.


Figure 3.b.2

Biomes determined by temperature and precipitation


In this lab we will explore how biomes are being altered due to human activities.


Introduction to Biomes


Desert and tundra biomes occupy the most extreme environments. Both have little or no moisture and extremes of temperature. Most deserts occur at 30o N or S latitude dry air masses descend. Tundra occurs near the Earth’s north and south poles or on high mountaintops. These two biomes have the lowest species richness due to the extreme environments in which they are found.



Figure 3.b.3

Biomes and wind patterns on Earth



Tropical rain forests occur in regions near the equator where the climate is warm and rainfall is high. The rain forest contains the greatest number of species and highest biomass of any biome. More than fifty percent of all terrestrial species live in this biome. Unfortunately, approximately 17 million hectares of rain forest are being destroyed every year due to deforestation. At the current deforestation rate, within 100 years these forests will have completely disappeared. Along with loosing a great deal of species diversity, this may have dramatic impacts on rainfall and climate patterns on Earth.


The temperate forest biome occurs south of the boreal forest or taiga in eastern Asia eastern North America, and in Europe. Rainfall for this biome is generally plentiful. Forests consist of deciduous (broadleaf trees that lose their leaves in the winter) and coniferous (needle leaf trees that generally keep their leaves in winter) species of trees.


The shrubland or chapparal biome is dominated by hearty evergreen shrubs that can survive the dry summers and frequent fires that occur in parts of South America, western Australia, central Chile, and around the Mediterranean Sea.


Grasslands occur in temperate and tropical areas with low rainfall or prolonged dry seasons. Soils in this region are deep and rich thus most of the grasslands on Earth have now been converted to agriculture.


The taiga or boreal forest extends across northern Eurasia and North America. The taiga receives ample rainfall but has a short growing season. Winters are cold and summers tend to be cool. This region stores a great deal of carbon in the soils and is predicted to warm the most due to global warming. This may cause a dramatic positive feedback effect and contribute to greater warming.



Figure 3.b.4

Map of Earth’s biomes


Exploring Forests and Agriculture


Open your Inquiries.mxd ArcGIS file. Save the file under a new name.


Copy the Forest Ecosystems theme and paste it at the top of the theme colunm (Right-click and select Copy, then Edit ŕ Paste). Double-click on the original Forest Ecosystems theme to open the layer properties window.  Under the Symbology tab, create a graduated color legend using Total forest area in 1000 ha (areaFor00) as the classification field value. Classify the legend by natural breaks into five classes and choose an appropriate color scheme and click on OK. 


For the new Forest Ecosystem theme, change the name to Forest Types under the general tab in layer properties and click Apply. Under the Symbology tab, change the legend type to Charts, and create a pie chart. Create a pie chart based on Table 3.b.1.


Table 3.b.1

Natural and plantation forest area


Classification Field

Abbreviated Name


Natural forest area


1000 ha

Plantation forest area


1000 ha


In the layer properties window (Figure 3.b.5), change the background to hollow. Decrease the maximum size of your pie chart to 12. Select an appropriate color scheme for the pie chart. You can alter each color by right-clicking on each symbol and choosing colors. When you are satisfied with you pie chart characteristics, click on OK. In the theme column, make sure that the Forest Types pie chart theme is above the Forest Ecosystem theme. Also within the theme column, you can change the names of the pieces of your pie chart by right-clicking, then left-clicking on the theme name.  The name should turn blue and allow you to type in the name of your choice.




Figure 3.b.5

Creating a pie chart



Use the Zoom tool  to examine individual countries or continents and use the pan function  to move around the globe and examine at different areas of the map. Use the globe symbol  to return to the full screen view after examining different areas of the world.


Question 3.b.1

What trends do you see in natural forests versus plantation forests around the world?


Turn the Forest Types and Forest Ecosystems themes off. Copy the Biodiversity theme and paste it at the top of the theme column. Within the layer properties window, under the General tab, name your new theme Forest Change and select Apply. Under the Symbology tab, create a graduated color map of the rate of forest change in percent per year by country. Use Percent Forest Change (Defor_rate) as your classification field value. Classify your data as seven natural breaks and choose the red to blue color ramp. Make sure zero forest change is a class on its own. This way, countries in the red to yellow spectrum have high forest loss, those in green will have no forest change (even deforestation with reforestation or zero net forest loss), and those countries in the blue spectrum will have forest gain or reforestation. Click on the OK button when you are finished.


Question 3.b.2

What trends do you see in rates of forest change around the world? Please be specific about which areas of the world are showing forest loss and speculate on why this might be occurring.


Copy your Forest Change theme and paste it at the top of the theme column. Name the new theme Threatened Plants. Within the legend properties window, under the Symbology tab, choose legend type dot density (Figure 3.b.6). Choose Number of Threatened Plants (Plant_thr = number of plants threatened with extinction) as the dot density field. Click on the each name within the Field Selection window to see the entire name displayed. For the dot value, choose 1 dot= 1 (threatened plant). This means that for every dot that you see on the map it represents one species of plant threatened with extinction. Make sure that your background symbol is transparent and your dot size is 2. Right-click on the symbol (dot) to change the color of the dots to black, then click on the OK button.




Figure 3.b.6

Creating a dot overlay


Question 3.b.3

Which regions of the world have the greatest number of threatened plants? How does the rate of forest change correspond with threatened plants?


Create a jpeg picture of Africa with Threatened Plants overlaid on Forest Change. To do this, copy each theme and paste them at the top of the theme column and turn the original themes off. This way you will still have a copy of the original theme after you have created your query. Rename the new themes Threatened African Plants and African Forest Change For each of the new themes double-click on the theme legend and go to the Definition Query tab. For each theme, build a query using Query Builder. First double-click on [Continent] then click on the equals sign.  Next, click on the Get Unique Values button and double-click on ‘Africa’ to complete your query which should read, [Continent] = ‘Africa’. Your map should now be limited to the African continent. Make sure that Threatened African Plants is at the top (drag it to the top if not) and that the Country theme is turned off.


Using the zoom and pan tools, position your continent in the center of your page. Next, go to View ŕ Layout View and your map should appear in a picture window. Insert an appropriate, title and legend using Insert.


Once you are happy with your layout, go to File ŕ Export. Under List Files of Type: choose JPEG. Choose a place to save your map and give it an appropriate filename. Once you have saved your map open up the JPEG to check the map. In your Word document, go to Insert ŕ Picture ŕ From File. Then navigate to your saved JPEG picture to import it into the Word document. It should look something like Figure 3.b.7.


Figure 3.b.7

Layout of African forest change and threatened plant species





Figure 3.b.8

Map of Earth’s biomes


Exploring Agricultural Pressures

Explore how increasing agricultural pressures may be altering different biomes. First turn off the maps you have created so far. Copy and paste the Agriculture theme at the top of the themes column. Rename the new theme Cereal Production Change. Create a red to blue color map of the Total Cereals Production Change since 1992 (zchcerlpro) by selecting this as your classification field value. Classify your data into seven natural breaks. Click on the classify button and change the fourth break value to zero. This will change the scale of your legend so the red to yellow spectrum are negative (a decrease in cereal production), the green symbol is near zero (no change in cereal production since 1989-1991), and the blue colors are positive (increase in cereal production over time) as you did for Forest Change.


Question 3.b.4

What trends do you see in the cereal production since 1992? Why might there be missing data for the countries in the former Soviet Union?


Copy your Forest Change theme and paste it above Cereal Production Change. Classify your data into 3 natural breaks. Click on the classify button and make your break values -1, 0 and 10 and click OK. Then right-click on each symbol in Forest Change and choose properties for selected symbol(s). Next, alter each symbol so that it is density dependent on the rate of forest change. For example in the –9 to –1% forest loss category, choose the black 10% crosshatch pattern. Next, select scrub 1 for the zero net forest change category, and choose black for the fill color, and black for the outline color. Next, click on the properties button and select no color for the background color. Use the black 10% ordered stipple category for the positive forest change or forest gain category. For the stipple pattern, make sure that your background is transparent by clicking on the properties button and selecting no color for the background. This map will allow you to see if percent forest change and percent change in cereal production are related.


Question 3.b.5

Do you see a relationship between the rate of forest change and the change in cereal production since 1992? What might be happening in countries that do not follow the same pattern?


Turn off the Forest Change theme. Copy the Forest Ecosystem theme and paste it at the top of the theme column. Double-click on the theme and open the layer properties window. Under the general tab, rename the new theme Grasslands and select Apply. Click on the Symbology tab, under quantities select dot density. Define this map using Area grasslands in 1000 ha in 1992 (Argraslnd) as the density field. In the dot value make 1 dot = 5,000. This means that for every dot shown it represents 5,000,000 hectares of grassland. Next, right-click on the dot symbol and change the dot color to black. Make sure that the Grasslands theme is above Cereal Production Change. This map should give you a sense of where the grasslands on Earth were found in 1992 and how that might relate to changes in cereal production over time.


Question 3.b.6

How do the distribution of the Earth’s grasslands relate to changes in cereal production? Where do you see exceptions to this pattern?



The Future of Threatened Biomes


Now explore the global status of the Earth’s biomes. Turn off all themes used up until this point and activate the Biomes theme.



Figure 3.b.9

ArcGIS map of Earth’s biomes


Copy the Biomes theme and paste it at the top of the theme column. Rename the new theme Biome Status. Within the layer properties, select Global Status (GBL_STAT) as the Classification Field Value. The global status gives us a 30-year prediction of future conservation status given current conservation status and trajectories.


Classify the data into 4 natural breaks and define your null value (no data class) as 0 (zero) and make it gray by double-clicking in the symbol or right-clicking on the symbol and selecting Properties of selected symbol(s). Next, type the category labels in the legend as defined in table 3.b.2.


Table 3.b.2

Global status of Earth’s biomes



Global Status Key

0 = No Data

1 = Critical or Endangered

2 = Vulnerable

3 = Relatively Stable or Intact


Double-click on the critical-category symbol and choose black 10% crosshatch. For the vulnerable category, choose black 10% stipple dots. Make sure that the background has no color for this category. For the intact category, choose hollow.


Make sure that the Biome Status theme is placed above the Biome theme and make sure that both themes are activated to examine the status of each biome. This theme incorporates a large amount of data so it may take some time to load. If your map stops loading uncheck and recheck your theme names and the map should appear. Use the zoom key to look at regions in more detail. The pan key is useful for moving around the map when looking at biome regions in detail.


If this overlay is too difficult for you to view you can create a second data frame and examine both maps concurrently. Choose Insert and select New Data Frame. Click on the new data frame and rename it Biome Frame.


Next, click on the Biome Status theme on the theme column and drag it down into the Biome Frame data frame. Alternatively, right click on Biome Status and select Copy, then select the Biome Frame data frame and choose Edit ŕ Paste. Deactivate the original Biome Status theme. Open the layer properties window of the Biome Status theme in the Biome Frame. Change the critical category to red and the vulnerable category to yellow and click on OK.


Next select View ŕ Layout View. The two data frames should appear with a set size in the middle of the layout page. The new frame should be highlighted with blue handles, indicting that it is the active frame. The active frame is also shown in boldface type in the theme column or table of contents. Next, resize both frames so they are the same size and do not overlap on the page. Use the Zoom tool to enlarge the maps inside the layout frame box.


Next, set the map projection of the new frame so that the new frame can have the same projection with the Inquiries In Global Change frame. Right-click on the Biome Frame data-frame and choose properties from the menu.  Select the Coordinate System tab, and in the box showing the coordinate system trees, click the following links to find the coordinates system desired: Predefined > Projected Coordinate System > World > Flat Polar Quartic (world). Click OK. You will get warning but just click on the Yes button. You should be able to see the Biome Frame data frame map change shape to match the Inquiries In Global Change data frame map. Examine the status of each of the 14 biomes as in Figure 3.b.10.




Figure 3.b.10

Layout view of Biomes of the world and their status




Question 3.b.7

Based on the status of each biome, which biomes do you think are most at risk from human pressures? Which biomes should receive priority for conservation? Why? What strategies could be implemented to better protect Earth’s biomes?


Question 3.b.8

Using the Biome Status theme overlaid on the Biomes theme, or by using two data frames to compare Biomes and Biome Status maps simultaneously, create a JPEG layout (like you did for Africa earlier in the lab) of the continent or region that includes some of the biome that you think should receive priority for conservation. To accomplish this, use the layout view and zoom in on the region that includes the biome you selected for conservation. Make sure that your layout includes titles, legends, your name and any other relevant information.




Major terrestrial biomes. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com).







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