The effectiveness of Payments for Ecosystem Services at delivering improvements in water quality: lessons for experiments at the landscape scale.
The effectiveness of Payments for Ecosystem Services at delivering improvements in water quality: lessons for experiments at the landscape scale.
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作者：
Pynegar EL;Jones JPG;Gibbons JM;Asquith NM
随机对照试验 (RCT) 用于一系列领域的影响评估。然而，尽管人们呼吁在环境管理中更多地使用它们，但它们用于评估景观规模干预措施的情况仍然很少。生态系统服务付费（PES）激励土地使用者管理土地以提供环境效益。我们对旨在改善水质的 PES 计划进行了首次 RCT 评估。 Watershared 是一项激励土地所有者避免森林砍伐并将牛群排除在河岸森林之外的计划。通过这一不寻常的景观规模实验，我们探索了 Watershared 在改善水质方面的功效，并为未来景观规模环境管理干预措施的 RCT 评估吸取经验教训。 2010 年收集基线数据（包括大多数社区的大肠杆菌污染）后，玻利维亚安第斯山脉的 129 个社区被随机分配到治疗组（提供水共享协议）或对照组（未提供协议）。我们于 2015 年收集了最终数据。利用最终数据，我们探讨了与干预措施相关的变量（例如排除牛、没有粪便）预测当地水质的程度。然后，我们使用随机对照试验研究了干预措施在景观尺度上改善水质的效果。该分析通过两种方式完成；对于我们拥有来自相同地点的基线和终线数据的社区子集，我们使用双重差异（与基线水质匹配），对于所有地点，我们比较了选定水质预测因子的终线控制的控制和处理。水中牛粪便的存在对水质产生了不利影响，这表明排除牛对当地水质有积极影响。然而，匹配的双重差异分析以及终线处理群落和对照群落之间的比较都表明，Watershared 不能有效减少景观尺度上的大肠杆菌污染。水资源共享协议的采用率非常低，从水质角度来看最重要的土地（取水口周围的土地）很少被纳入。尽管排除牛可能对当地水质产生积极影响，但需要更高的吸收率和更好的针对性才能对社区用水质量产生重大影响。尽管 RCT 在为 PES 等方法建立证据基础方面可能发挥重要作用，但实施起来却远非易事。在这种情况下，随机试验并不是得出 Watershared 未产生景观规模影响的结论的核心。我们建议，这项随机对照试验为未来使用随机实验来评估景观规模的环境管理干预措施提供了宝贵的经验教训。
Randomised Control Trials (RCTs) are used in impact evaluation in a range of fields. However, despite calls for their greater use in environmental management, their use to evaluate landscape scale interventions remains rare. Payments for Ecosystem Services (PES) incentivise land users to manage land to provide environmental benefits. We present the first RCT evaluation of a PES program aiming to improve water quality. Watershared is a program which incentivises landowners to avoid deforestation and exclude cattle from riparian forests. Using this unusual landscape-scale experiment we explore the efficacy of Watershared at improving water quality, and draw lessons for future RCT evaluations of landscape-scale environmental management interventions. One hundred and twenty-nine communities in the Bolivian Andes were randomly allocated to treatment (offered Watershared agreements) or control (not offered agreements) following baseline data collection (including Escherichia coli contamination in most communities) in 2010. We collected end-line data in 2015. Using our end-line data, we explored the extent to which variables associated with the intervention (e.g. cattle exclusion, absence of faeces) predict water quality locally. We then investigated the efficacy of the intervention at improving water quality at the landscape scale using the RCT. This analysis was done in two ways; for the subset of communities for which we have both baseline and end-line data from identical locations we used difference-in-differences (matching on baseline water quality), for all sites we compared control and treatment at end-line controlling for selected predictors of water quality. The presence of cattle faeces in water adversely affected water quality suggesting excluding cattle has a positive impact on water quality locally. However, both the matched difference-in-differences analysis and the comparison between treatment and control communities at end-line suggested Watershared was not effective at reducing E. coli contamination at the landscape scale. Uptake of Watershared agreements was very low and the most important land from a water quality perspective (land around water intakes) was seldom enrolled. Although excluding cattle may have a positive local impact on water quality, higher uptake and better targeting would be required to achieve a significant impact on the quality of water consumed in the communities. Although RCTs potentially have an important role to play in building the evidence base for approaches such as PES, they are far from straightforward to implement. In this case, the randomised trial was not central to concluding that Watershared had not produced a landscape scale impact. We suggest that this RCT provides valuable lessons for future use of randomised experiments to evaluate landscape-scale environmental management interventions.
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影响因子：
6.6
作者：
Bruijnzeel, LA
通讯作者：
Bruijnzeel, LA
DOI：
10.1016/j.cosust.2015.06.001
发表时间：
2015-06-01
影响因子：
7.2
作者：
Calvet-Mir, L.;Corbera, E.;Gross-Camp, N.
通讯作者：
Gross-Camp, N.
影响因子：
4.4
作者：
Ahmed, W.;Hodgers, L.;Toze, S.
通讯作者：
Toze, S.
影响因子：
15.8
作者：
Bain R;Cronk R;Wright J;Yang H;Slaymaker T;Bartram J
通讯作者：
Bartram J
影响因子：
7
作者：
Bottazzi, Patrick;Wiik, Emma;Jones, Julia P. G.
通讯作者：
Jones, Julia P. G.