Ecological Archives E096-112-A4

Rafael X. De Camargo and David J. Currie. 2015. An empirical investigation of why species–area relationships overestimate species losses. Ecology 96:1253–1263. http://dx.doi.org/10.1890/13-2362.1

Appendix D. The proportion of human-dominated land cover that is available for bird species explained by remote-sensed land cover types.

Our analysis showed that there is an important amount of habitat that is available to open-habitat bird species in a landscape of 100km² in southern Ontario. The available habitat is positively correlated with the amount of remotely sensed land cover in all human-dominated classes (Table D1). Cropland land cover, which corresponds to 34% of the total land cover in southern Ontario and to 76% of the human-dominated land cover, is the main contributor to the availability of human-dominated habitat used by bird species (see Beta-coefficients, Table D1). The amount of cropland in each BBA quadrat is responsible for 45% of the variability found in the proportion of habitat that is available for birds (linear regression, F = 820.6, R²adj = 0.45, p < 0.0001). However, the relationship between human-dominated habitat that is available and cropland amount is peaked (Fig. D1).

Table D1. The results of a multiple regression predicting the proportion of human-dominated habitat (Ahuman_avail) that is available for bird species in 100 km² quadrants southern Ontario (estimated empirically from the species richness of open-habitat birds) as a function of the amount of remotely-sensed land cover in various categories (R² = 0.85, n = 991 squares). All coefficients are statistically significant, p < 0.0001.

Ahuman_avail categories

Coefficients

Beta-coefficients

t value

Recent cutovers

0.64

0.14

11.00

Mining tailings

0.49

0.24

19.62

Urban Areas

0.14

0.09

7.44

Pasture and fields

0.87

0.63

50.00

Croplands

0.25

0.75

57.5

 

FigD1

Fig. D1. The peaked relationship between the proportions of habitat that is available for avian species and human-dominated (Ahuman) land cover that is composed by crops fitted with a lowess smoothing line.


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