Table 3. GLM model results (slope coefficients and associated ± SE) of predictors of cumulative vegetation (forest and cerrado) conversion rate as of 2011 within agrarian settlement areas across the Brazilian Legal Amazon region (N = 1,911); and mean difference in annual deforestation rate before (until year–1) and after (since year+1) the creation of settlements (N = 300).
| Vegetation conversion rate | Δ Post:Pre deforestation a | ||||
|---|---|---|---|---|---|
| Model components | Units | Global | Best b | Global | Best b |
| Total settlement area | Hectares (log10 x) | –0.355 ± 0.019 ** | –0.346 ± 0.115 ** | –0.373 ± 0.180 * | –0.380 ± 0.122 ** |
| Human population density of settlement | Families km-2 (log10 x) | 1.202 ± 0.212 *** | 1.149 ± 0.209 *** | 0.035 ± 0.279 | |
| Settlement occupation capacity shortfall | (predicted family capacity—number of families settled) km-2 (log10 x + 1) | –0.028 ± 0.363 | –1.115 ± 3.307 | ||
| Age of settlement c | Years since establishment (sqrt x) | 0.013 ± 0.050 | NA | NA | |
| Soil fertility | Weighted mean soil fertility index | 0.076 ± 0.052 † | 0.250 ± 0.065 *** | 0.254 ± 0.063 *** | |
| Pre-settlement forest cover d | Forest cover (%) in settlement polygon remaining in the year prior to settlement establishment (yr–1) | NA | NA | 1.478 ± 0.202 *** | 1.523 ± 0.197 *** |
| Distance to nearest road | km (log10 x + 1) | –0.143 ± 0.032 *** | –0.141 ± 0.032 *** | 0.049 ± 0.046 | |
| Traffic intensity of nearest road | Mean flow rate of heavy vehicles (trucks and buses) per day (log10 x) | 0.271 ± 0.049 *** | 0.272 ± 0.050 *** | 0.214 ± 0.071 *** | 0.223 ± 0.070 *** |
| Model deviance explained (%) | 15.67 | 15.48 | 22.20 | 21.88 | |
| Model AICc | 1994.4 | 1995.8 | 962.6 | 957.8 | |
a Refers to the difference in mean annual rate of forest loss before (t ≤ yr–1) and after (t ≥ yr+1) the onset of agrarian settlements (see text). Age of settlement was therefore omitted from these models.
b Most parsimonious model selected based on multiple comparisons of AIC values.
Significance levels:
† < 0.10,
* < 0.05,
** < 0.01,
*** < 0.001.
c Omitted from Δ Deforestation models because our before-and-after deforestation rate already considers the settlement time trajectory;
d Omitted from vegetation conversion rate models due to data unavailability for all but the 300 settlement polygons for which Δ Deforestation models were performed.