manual for social impact assessment of land-based ... - Forest Trends

Example
The first documented application of the PEV or contingent valuation method involved a group of small
farmers in Zimbabwe estimating a range of environmental and subsistence benefits from an
agroforestry project (Campbell et al., 1991). The farmers were asked to rank and score 10 benefits from
multi-purpose agroforestry trees against the value of a hand-pump borehole (the numeraire).
As part of a household survey, 10 cards were laid out before each respondent, each card representing
an agroforestry benefit. Also, two cards representing ‘anchor values’ were handed out: a hand borehole
and a ‘Blair’ latrine. Each respondent was then asked to place 50 matches on the 12 cards (using the
proportional piling technique). They were then asked what they would be prepared to pay to have the
(hypothetical) opportunity of joining four other households in sinking a borehole and installing a hand
pump, with success guaranteed and an interest-free loan to be paid back over 5 years. This represented
their WTP for their share of the borehole. They were also asked for their choice between a share of the
borehole and five specified commodities ranging in value from Zim $90 to Zim $ 35,000.
The number of matches scored by each category of benefit was then standardised against the number
of matches allocated to the borehole. Thus each benefit was expressed in terms of its borehole
equivalent, and multiplied by the WTP borehole value. This resulted in the values shown in Table T18.
The discounted annual benefit was estimated in the range of Zim $84-336 per household.
Table T18: Estimated Value of Agroforestry Benefits in Zimbabwe
Benefit (Good or Service) Mean WTP value - Zim $ Median WTP value - Zim $
Fuel 373 500
Farm/house materials 290 400
Crop production 222 333
Animal feed 181 144
Nutrient recycling 175 257
Food 136 200
Shade 102 150
Cash income 82 125
Health 71 100
Social benefits 46 47
Note: At the time of the study, there were Zim $3.13 per US dollar.
Source: Campbell et al., 1991.
Social Impact Assessment of Land-Based Carbon Projects (1.0) – Part II | 63