The housing density/sprawl area trade-off

Increasing housing density has negative effects on native biodiversity. This implies that we should build at low density to conserve native species. However, for a given human population, low-density development must cover a large area, resulting in sprawl. A pertinent question is then, at what housing density are the impacts of a given human population on native biodiversity minimized? For a given human population, it is unclear whether the impacts on forest biodiversity are less where housing density is high and sprawl area is small or where housing density is low and sprawl area is large.

 

We used empirical data on breeding bird and carabid beetle communities to estimate bird and beetle species richnesses and abundances in hypothetical development scenarios representing the housing density/sprawl area trade-off.

Figure 3 for trade-off sub-page

 

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Our results suggest that clustering development at a high housing density (i.e., building compact development) minimizes the impacts of a given human population on forest bird and carabid beetle communities (see the results below and Gagné and Fahrig (2010a) and Gagné and Fahrig (2010b) for more information). If these results are general across all forest taxa, then planning that favors densification rather than sprawl would minimize urbanization effects on forest biodiversity.

 

Estimates of the abundance, species richness and evenness of three bird groups in four hypothetical development scenarios: U, Undeveloped; D, Dispersed; SC, Semi-compact; C, Compact. The lower edge of each box is the first quartile, the bold center line is the median and the upper edge is the third quartile of the distribution. Whiskers extend to the minimum and maximum values.

forest

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The estimated abundances of five carabid beetle groups in four hypothetical development scenarios: U, Undeveloped; D, Dispersed; SC, Semi-compact; C, Compact. (A) All beetles. (B) Forest beetles. (C) Open-habitat beetles. (D) Native beetles. (E) Non-native beetles. The lower edge of each box is the first quartile, the bold center line is the median and the upper edge is the third quartile of the distribution. Whiskers extend to the minimum and maximum values.

beetles

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The estimated species richnesses of three carabid beetle groups in four hypothetical development scenarios: U, Undeveloped; D, Dispersed; SC, Semi-compact; C, Compact. (A) All beetles. (B) Forest beetles. (C) Open-habitat beetles. The lower edge of each box is the first quartile, the bold center line is the median and the upper edge is the third quartile of the distribution. Whiskers extend to the minimum and maximum values.

beetles 2

 

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