ENV100Y5Y Assignment #3
CARBON CYCLING IN THE TERRESTRIAL ECOSPHERE
Due before 5:00 p.m. on Friday, February 18, 2011.
This assignment will give you the opportunity to interpret graphs and carry out some simple
calculations based on environmental data, then draw conclusions on the basis of those
We will be using an exercise like this in the new edition of the textbook, Environment: The
Science Behind the Stories, and I will be happy to have your reactions to the assignment. (In the
book it will not include multiple-choice questions, rather written-answer questions for those
sections, but we need to use multiple-choice for ease of submission to Blackboard.)
Please download and work through the assignment ―offline‖ – it should take you about 20
minutes. If you need help, please consult with Varun during his office hours or make a special
appointment to meet with him.
Then, when you are ready, submit your answers in the Assignment #3 folder on our course
Blackboard site. You will be able to save your work and return to it on Blackboard, but please
don’t hit ―Submit‖ until you are ready, as we won’t be allowing multiple submissions (it makes
the marking much more complicated).
Interpreting Graphs and Data
Dr. Henry Janzen is a soil scientist at the Lethbridge Research Centre in Alberta, and an Adjunct
Professor at the University of Manitoba. He is an expert on carbon cycling and the emission of
greenhouse gases from soils, and he carries out research on the effects of different management
approaches on carbon storage in agricultural soils. In a 2004 paper in the journal Agriculture,
Ecosystems and Environment, Dr. Janzen summarized many of the main scientific questions
concerning carbon storage in terrestrial reservoirs. One concern outlined in Dr. Janzen’s study was the impact of land-use changes on carbon
storage in terrestrial reservoirs. The following figure from the paper summarizes major land-use
changes since 1700:
This graph shows the change in terrestrial area for three groups of major biome types, and the increase in
area of pasture and croplands since 1700. Figure 2 from Janzen, H.H. (2004), Carbon cycling in earth
systems—a soil science perspective. Agriculture, Ecosystems and Environment 104, 399-417, plotted
from values in Goldewijk, K.K. (2001), Estimating global land use change over the past 300 years: the
HYDE database. Global Biogeochem. Cycles 15 (2), 417-433.
The first three questions are based on the graph shown above. For all questions, please consider
pasture and cropland combined.
1. On the basis of the graph, which of the natural biome types (forest/woodland,
steppe/savannah/grassland/shrubland, or tundra/desert) or managed ecosystems
(pasture/cropland) increased the most, in terms of percentage increase, from 1700 to
2. Which one of the biomes or managed ecosystems decreased the most, in terms of
percentage decrease? 3. What happened to the area covered by tundra/desert over the time period represented on
The table below presents some information ab