Definition of the Environmental Benefits Index
The term Environmental Benefits Index (EBI) was inspired by the USDA Conservation Reserve Program as a programmatic rule for ranking the cost-effectiveness of land units bidding for program participation. The scoring procedure uses an arbitrary but plausible and simple-to-implement point system. The highest points are assigned to mature forest and to wetlands. Secondary forest and shade cocoa/cabruca are assigned moderate point values if located in the same land unit as mature forest, because they then offer good prospects for forest regeneration. Otherwise secondary forest and shade cocoa/cabruca receive a lower score.
EBI was defined as follows:
EBI = [1000/(per-hectare land value)]*
[5 * P_mature +
5 * P_wetland +
3 * P_cabruca * D(P_mature) +
3 * P_secondary * D(P_mature) +
1 * P_cabruca * (1 - D(P_mature)) +
1 * P_secondary * (1 - D(P_mature))]
where D(x) = 0 if x = 0
D(x) = 1 if x > 0
P_mature = proportion of planning unit in mature forest
P_cabruca = proportion of planning unit in cabruca and other tree shaded cocoa
P_secondary = proportion of planning unit in secondary forest
where land value and land cover proportions are calculated for the part of a land unit that is not urban, water-covered, or in a protected area.
Land cover transition rules
Lacking a quantitative, behavioral model for land use change in Bahia, the authors employed a simple deterministic model of change, assuming continuation of current trends over a notional period of two decades. A transition matrix specified future land cover under two different states for the land unit: business-as-usual, and protected status (i.e. under conservation easement). Selection into protection places all vegetation into ‘regenerating forest’ status. Regeneration is costless (due to assumed seed sources) except for pasture/agriculture pixels that are not in the same land unit as mature or secondary forest; for these areas a reforestation cost is incurred.
In the business-as-usual scenario we assume that, despite legal regulations against clear-cutting or degradation of forest, mature forest will be degraded gradually into secondary forest through timber and firewood extraction and agricultural encroachment. Secondary forest will be permanently converted to pasture or agriculture except in areas where it is near mature forest; in such situations, it will remain secondary forest. In the business-as-usual state, the fate of cabruca and other tree shaded cocoa culture depends on local agronomic conditions. Cabruca will be partly replaced by other forms of agriculture except in areas where previously established on soils with the highest agricultural production capacity (prime farmland), on steep terrain (larger than 70% slope) or on floodplains. For convenience of processing, surviving cabruca and other tree shaded cocoa was reclassified to secondary forest, because we assume that it has the same properties buffering edges and facilitating gap crossing. Pasture and agriculture will remain unchanged, because we assume no spontaneous abandonment and regeneration of farmland. Bare land is assumed to be a temporary state of agricultural land that is reclassified as agriculture/pasture for the future. Urban land uses and other habitat types (e.g., mangrove, wetlands, water bodies) cannot be converted into forest and are assumed to remain in their present condition. Similarly, we did not anticipate changes for restinga and caatinga. For a summary of all rules see the table below.