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Wood Use: How Big Is an Acre? Activity
In much of the controversy surrounding deforestation, all kinds of numbers are being thrown around. Sometimes they are comforting, sometimes they are scary. Often, groups are fighting for our emotions when they present data to us. Sometimes, they are more interested in making an emotional impression rather than an accurate one.

Frequently the data presented deal with number of acres. In many cases, the number of acres or hectares involved actually are something most of us can't picture. The objective of this exercise is to help you get a sense of how big different areas are so you will be better prepared to evaluate the validity of the measurements posed by each side of an issue.

Here's an example of conflicting data from the tropical rainforest debate:

  1. In "The Olympic Rain Forest: An Ecological Web" (1992, p. 41), Ruth Kirk, a nature writer, and Dr. Jerry Franklin, former chief plant pathologist for the U.S. Forest Service say, "Thirty acres of tropical trees fall every minute."
  2. In "Forest Resources Assessment 1990: Tropical Countries" the United Nations Food and Agricultural Organization, presents data that when you do the math, come out to 21.6 acres of tropical trees cut every minute. That's a little more than 25% disagreement with Kirk and Franklin.
  3. On their Kids Page, the Rainforest Action Network (RAN), report, "In fact, rainforests are disappearing at frightening speed: 150 acres per minute..."

Whoa! RAN disagrees with Kirk and Franklin by a factor of 5. That's a disagreement of 500%! And RAN disagrees with the United Nations by a amazing 694%. At this point you may not know who to believe. Disagreements this large should set off some alarm bells and make you question the accuracy of the data.

How big is big? The following data may help:

1 acre =  43,560 square feet
1 acre = 0.405 hectares (the unit most countries use)
640 acres = 1 square mile
1 hectare = 2.471 acres (you can round it to 2.5 if you are doing math in your head)
100 hectares = 1 square kilometer

Some comparisons:

How big is the site your school is on? __________________ acres __________________ hectares
How big is an American football field (including the end zones) __________________ acres __________________ hectares
If you live in a city, how big is a city block? __________________ acres __________________ hectares
How big is your town? __________________ acres __________________ hectares
If you have a favorite park or natural area where you live, how big is it? __________________ acres __________________ hectares
How big is your county? __________________ acres/hectares __________________ sq. mi./sq. km.
How big is your state or province? __________________ acres/hectares __________________ sq. mi./sq. km.
If there is a national park you are familiar with, how big is it? __________________ acres/hectares __________________ sq. mi./sq. km.

These comparisons may help you visualize data. For example, Kirk and Franklin's data claims rainforests are being cut down at the rate of 30 acres every minute. That is comparable to cutting down between 9 and 10 football fields' worth of trees every minute. That's a lot of trees!

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