FORUM The tangled causes of population decline in two harvested plant species: a comment on Ticktin et al. (2012) Soumya Prasad 1,2,3 *, Meghna Krishnadas 4 , Kim R. McConkey 3,5 and Aparajita Datta 6 1 TE-13, Biological Sciences Building, Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560055, India; 2 Nature Science Initiative, 36 Curzon Road, Dehradun 248001, India; 3 School of Natural Sciences and Engineering, National Institute of Advanced Studies, Indian Institute of Science Campus, Bangalore 560055, India; 4 Department of Evolution, Ecology and Organismal Biology, Ohio State University, 318 W. 12th Avenue, Columbus, OH 43210-1293, USA; 5 A.V. Rama Rao Research Foundation, 54 Sai Enclave, Hyderabad 500 007, India; and 6 Nature Conservation Foundation, 3076/5, IV Cross, Gokulam Park, Mysore 570 002, India Summary 1. Ticktin et al. (2012) attempted to disentangle multiple stressors impacting harvested popu- lations of amla (Phyllanthus emblica and P. indofischeri) [Ticktin et al. (2012) Disentangling the effects of multiple anthropogenic drivers on the decline of two tropical dry forest trees. Journal of Applied Ecology, 49, 774–784.]. 2. We propose that an unbalanced design and substitution of missing data for key parame- ters render their matrix models flawed. They conclude that the main threats to recruitment were lantana and mistletoe invasion and recommend revoking the ban on amla harvest. 3. Our re-analyses of their data set, without substituting unavailable data, showed that cessa- tion of harvests significantly increased stochastic growth rates of amla, despite high lantana and mistletoe cover. 4. Management recommendations by Ticktin et al. (2012) were based on the assumptions of invasiveness of a native mistletoe and grazing impacts of wild ungulates. However, interac- tions with amla are complex, and the recommendations made by them could have deleterious repercussions on native biota. 5. Synthesis and applications. Developing an objective understanding of harvest consequences by incorporating earlier findings and considering uncertainties in results is critical for main- taining livelihoods and ecological processes linked to amla populations. Key-words: amla, harvest, invasion, lantana, mistletoe, NTFP, Phyllanthus emblica Introduction Harvesting of non-timber forest products (NTFP) from native ecosystems supports livelihoods of local communi- ties in many parts of the world (Panayotou & Ashton 1992), but its ecological sustainability is often contentious (Siebert 2004). Comprehensive assessment of sustainability is challenging since it involves monitoring a suite of parameters, at genetic, population, community and landscape levels, across multiple generations, and inclu- sion of social, economic and political drivers (Shahabud- din & Prasad 2004; Siebert 2004). While it is not possible for a single study to integrate all these parameters, applied research must be designed to ensure adequate pre- dictive power for assessments of sustainability. Studies examining the impacts of NTFP harvest have been cri- tiqued for a lack of objectivity (Siebert 2004). As an applied science that informs management of natural resources, NTFP studies must be methodologically rigor- ous, objectively test proposed models of conservation action and be specific in extrapolating results for manage- ment (Shaanker & Ganeshaiah 2010). The debate on ecological sustainability of forest pro- duce harvest has been enriched by extensive research on the amla (ibid) and Brazil nut systems (Peres et al. 2003) from tropical Asia and South America, respectively. Amla species Phyllanthus emblica Linn. and P. indofischeri *Correspondence author. E-mail: prasadsoumya@gmail.com © 2013 The Authors. Journal of Applied Ecology © 2013 British Ecological Society Journal of Applied Ecology 2014, 51, 642–647 doi: 10.1111/1365-2664.12170