Land Use Change


Any surface receiving the suns ray’s will absorb some of the energy and reflect the rest. Some interesting effects and consequences for land use are seen below. See sections 5 and 6 on Ecosystems. And Section 3 on Albedo.

There are three main categories of landscapes:

  • natural – forests, water bodies, tundra , natural meadows, grassland, bog
  • managed or changed – planted fields, cleared land, newly planted forests
  • “built” landscapes – roads, buildings, houses, parking lots, canals, trails, vehicles

Each colour and type of roof has a different albedo or reflectivity. Each agricultural crop and each forest type has a different albedo. Every change on the landscape made by humans changes the albedo. Natural changes such as snow cover and ice cover have a great effect on albedo.

In Ontario, forests were cleared to grow food. The warmest parts of Ontario now have about 3% forest cover left and they now produce the most food.

Increases in available heat act as a powerful trigger to start processes in the natural world such as germination and melting. Temperature increases can also trigger the shut down processes and systems through overheating or dehydration. The rate of evaporation of surface water and soil along with evapotranspiration from plants will increase with warmer temperatures. Plant growth rate may increase.

To help warm the soil sooner in the spring and to prevent flooding of crops, many farmers have installed drainage systems. Flexible slotted piping has been buried in a pattern in the field and water is drained to a channel, and later into a creek, by gravity. Draining the land gives the farmer more growing days.

Water requires more heat energy per gram to increase its temperature by one Celsius degree than any other substance. The specific heat of water is 1 and all other substances are less.

In sunlight, beach sand is always warmer than the water. The sand cools faster than the waterwhen the sun sets. This effect is also the reason that large bodies of water modify the climate of the land near them. The Great Lakes, for example. See Ontario sections for Temperatures.

Corn Heat units are another way of measuring this. Air temperatures are used.

Southern Ontario Average Annual Corn Heat Units (CHU) Map

Note that Corn Heat Units are in degrees Celsius. This accumulated value is calculated using the following conditions:

  • Start-up of corn growing season: where the mean daily temperature is > 12.8 oC for three consecutive days during the period May 11 to July 31.
  • End of the season: the first occurrence when the minimum daily temperature drops below -2.0 oC during the period August 1 to October 15.












Source: Integrated Assessment Mapping Project


  1. What degree of latitude is the southernmost point on this map of southwestern Ontario? The northernmost point? The total range of degrees of latitude?
  2. How many minutes is this in map time?

Changing dates of planting, fertilizing, and harvesting, along with a change in the demand for irrigation, will have to be part of adaptation of agriculture to climate change, especially in southwestern Ontario.












Source: MacIver, D. C. and H. Auld (2000). The Changing Atmosphere: Forest Biodiversity and Productivity in Ontario, Canada. 14th Conference on Biometeorology and Aerobiology, 14-18 August 2000, Davis, California. 260-261 pg.

ACTIVITY 2 Research

  • The map above represents land use status in 2000. Research the increase in area changed to residential development, that is the area now covered by “built” environment. Use air photos or municipal reports in one chosen part of this area or in your own area to determine the increase in built area since 2000. Option: use documentation earlier than 2000

Increases in temperatures increase the rate of evaporation from the soil and evapotranspiration from agricultural crops, managed forests, and all natural ecosystems.













  • Set up a specific heat experiment using the same volume of water, oil, sand, and soil in each of 4 similar test tubes. Put a similar thermometer in each to the same depth. Place all 4 test tubes at the same time into a larger beaker containing water at room temperature. Heat the large beaker and record the temperatures of each substance each minute. Graph these results using a separate line for each substance.

Land use change that replaces agricultural fields with new forests affects the reflection of sunlight by land surfaces. In Canada with significant periods of snow cover, this effect can be significant. That is because, in winter, high albedo snow-covered agricultural fields are replaced by lower albedo forest landscapes.

This can cause a regional warming influence that may be greater than the benefit of the carbon sinks provided by the new forests. Source: National Climate Change Process Sinks Table Report









ACTIVITY 4 Research

  1. What is the annual number of hectares of forest that are cleared in Canada vs. the number of hectares that are newly planted? In Ontario? (Reforestation)
  2. What is the annual number of hectares of fields or meadows that are planted with new trees in Canada? In Ontario? (Aforestation)
  3. What does TC/ha mean? How much carbon dioxide does this represent?


Leave a Reply