Forest fragmentation study. Ecologists classify the cause of forest fragmentation as either anthropogenic (i.e., due to human development activities, such as road construction or logging) or natural in origin (e.g., due to wetlands or wildfire).

Conservation Ecology (Dec. 2003) published an article on the causes of fragmentation for 54 South American forests. Using advanced high-resolution satellite imagery, the researchers developed two fragmentation indexes for each forest—one for anthropogenic fragmentation and one for fragmentation from natural causes. The values of these two indexes (where higher values indicate more fragmentation)

for five of the forests in the sample are shown in the table below. The data for all 54 forests are saved in the FRAG file.

Ecoregion (forest)

Anthropogenic Index Natural Origin Index Araucaria moist forests 34.09 30.08 Atlantic Coast restingas 40.87 27.60 Bahia coastal forests 44.75 28.16 Bahia interior forests 37.58 27.44 Bolivian Yungas 12.40 16.75 Based on Wade, T. G., et al. “Distribution and causes of global forest fragmentation.”

Conservation Ecology, Vol. 72, No. 2, Dec. 2003 (Table 6).

a. Ecologists theorize that an approximately linear

(straight-line) relationship exists between the two fragmentation indexes. Graph the data for all 54 forests.

Does the graph support the theory?

b. Delete the data for the three forests with the largest anthropogenic indexes, and reconstruct the graph of part

a. Comment on the ecologists’ theory.