Ecological Indicators 67 (2016) 504–516 Contents lists available at ScienceDirect Ecological Indicators jo ur nal ho me page: www.elsevier.com/locate/ ecolind A methodology to estimate national REDD+ reference levels using the Zero-Sum-Gains DEA approach Jichuan Sheng a,b,∗ , Zhuang Miao b,c , U. Aytun Ozturk a,d a Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, 219 Ningliu Road, Nanjing 210044, China b Institute for Urban and Environmental Studies, Chinese Academy of Social Science, 28 Shuguangxili, Beijing 10028, China c School of Economics and Management, Taizhou University, 100 Chunhui Road, Taizhou 225300, China d Business and Economic, Faculty of International Liberal Arts, Soka University, 1-236 Tangi-machi, Hachioji-Shi, Tokyo 1928577, Japan a r t i c l e i n f o Article history: Received 8 January 2016 Received in revised form 2 March 2016 Accepted 3 March 2016 Keywords: REDD+ Deforestation Carbon emission Zero-Sum-Gains DEA Model Reference levels a b s t r a c t REDD+ reference levels directly impact the benefits which a country may receive. However, the existing “Compensation Reduction” (CR) and “Compensated Successful Efforts” (CSE) are only considered from a unilateral perspective of outputs or inputs. The combination of these two approaches is considered to estimate the REDD+ reference levels through the Zero-Sum-Gains Data Envelopment Analysis in this paper. The agricultural labor force and agricultural land area are used as input variables, and the gross agricultural production and carbon emissions from deforestation are considered as output variables. The REDD+ reference levels of 89 countries are calculated and classified through the Zero-Sum-Gains DEA model. The results demonstrate that the REDD+ reference levels are estimated efficiently through the Zero-Sum-Gains DEA model, and all countries with deforestation are in the Zero-Sum-Gains DEA frontier, indicating the overall Pareto optimality has been achieved. The empirical results also indicate that the use of Zero-Sum-Gains DEA model is more beneficial for Latin American and the Caribbean, while the countries that may see a revenue drop in REDD+ are in Africa, Asia and Oceania. Consequently, the final REDD+ reference levels should take into account both efficiency and fairness by selecting the appropriate fairness-efficiency weighting factor. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction 1.1. Evolution of reducing emissions from deforestation and degradation-plus (REDD+) Tropical forests account for approximately 15 percent of the planet’s land surface (FAO, 2010), yet absorb roughly 25 percent of the terrestrial biosphere carbon (Bonan, 2008). A decrease in this forest area has become one of the major culprits of global warm- ing. For instance, greenhouse gas emissions caused by deforestation and forest degradation have accounted for 12–20 percent of the total carbon emissions caused by anthropogenic factors (Sala et al., 2000; Houghton, 2008). Because this forest area is decreasing at an annual rate of 13 million hectares in tropical forest countries (FAO, 2010), the United Nations Framework Convention on Climate Change (UNFCCC) introduced a low-cost mitigation mechanism to assist developing countries in reducing deforestation and forest ∗ Corresponding author. Tel.: +86 138 1391 9570. E-mail address: shengjichuan@gmail.com (J. Sheng). degradation in 2007. This program is called “REDD” and although it was introduced in 2007, it was first proposed much earlier in 2005. It was further expanded upon in REDD+, which was defined by the Bali roadmap, adapted at the United Nations Climate Change Con- ference in 2007. REDD+ involves implementation of a variety of policy approaches and incentive plans to help developing (Non- Annex I) countries reduce deforestation and forest degradation, as well as forest conservation, sustainable management of forests and the enhancement of forest carbon stocks (UNFCCC, 2010). REDD+ signifies a stronger commitment to protecting common interests of biodiversity, equitable treatment of carbon storage and human livelihoods (Rosendal and Andresen, 2011). In addition, to further support national REDD+ strategies, the FCPF (World Bank Forest Carbon Partnership Facility) and UN-REDD have been established in July 2008 and September 2008 respectively. 1.2. Existing solutions and unsolved issues REDD+ aims to provide assistance to those countries, which are willing and able, in reducing the emissions caused by defor- estation, and also provide the necessary financial means (Scholz http://dx.doi.org/10.1016/j.ecolind.2016.03.010 1470-160X/© 2016 Elsevier Ltd. All rights reserved.