Forest Ecology and Management 324 (2014) 117–125 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco Can overharvesting of a non-timber-forest-product change the regeneration dynamics of a tropical rainforest? The case study of Euterpe edulis ⇑ Ana Elena Muler a, Débora C. Rother b, , Pedro S. Brancalion c, Rafaela P. Naves a, Ricardo R. Rodrigues a, Marco A. Pizo d a Departamento de Ciências Biológicas, ESALQ – Universidade de São Paulo (USP), Av. Pádua Dias, 11, Caixa Postal 9, Piracicaba, CEP 13418-900 São Paulo, Brazil b Programa de pós-graduação em Biologia Vegetal, Campus Rio Claro – Universidade Estadual Paulista (UNESP), Av. 24A, 1515, Caixa Postal 199, CEP 13506-900 Rio Claro, São Paulo, Brazil c Departamento de Ciências Florestais, ESALQ – Universidade de São Paulo (USP), Av. Pádua Dias, 11, Caixa Postal 9, Piracicaba, CEP 13418-900 São Paulo, Brazil d Departamento de Zoologia, UNESP – Universidade Estadual Paulista ‘‘ Júlio de Mesquita Filho’’ (UNESP), Av. 24-A, 1515, Bela Vista, CEP 13506-900 Rio Claro, São Paulo, Brazil article info abstract Article history: The exploitation of non-timber forest products is often considered a low-impact activity in tropical for- Available online 7 October 2013 ests. However, assessments of the impacts of such activity are mostly focused on the harvested species and not on the plant community, thus limiting our understanding for establishing forest management Keywords: recommendations. We investigated the consequences of Euterpe edulis palm heart harvesting on the seed Seed rain rain in the Brazilian Atlantic rainforest. We compared the density of E. edulis individuals, as well as the Seed dispersal density of E. edulis seeds, and the density, richness and functional composition of seed rain of the whole Keystone species plant community, before and after palm heart harvesting in a 10 ha permanent plot. This assessment was Harvesting carried out in preserved (typical old-growth Atlantic rainforest) and in disturbed (more open habitat Forest succession dominated by the native bamboo Guadua tagoara) forest patches. Palm harvesting reduced the E. edulis population from 202.16 to 25.67 ind/ha and its seed rain density from 0.362 to 0.3 seeds/m2 and from 2.395 to 0.15 seeds/m2 in preserved and disturbed forest patches, respectively. Seed density of light- dependent climbers, pioneer trees, bamboo and animal-dispersed seeds increased after palm harvesting, especially in the disturbed forest patches, where palm harvesting was more intense and may have chan- ged the light regime of the understory. On the other hand, species richness of the plant community declined by half. We observed a remarkable decline in the number of animal-dispersed species, especially for those with large seeds, suggesting that the activity of seed dispersers, including many species attracted by E. edulis fruits, was reduced. Therefore, harvesting of E. edulis palm heart may change the regeneration dynamics of the Atlantic rainforest, both due to shifts in forest structure, mediated by the removal of individuals from the forest canopy, and in community functioning, mediated by the interfer- ence on the activity of seed dispersers. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction management on the regeneration dynamics of ecological commu- nities and ecosystems (Ticktin, 2004;Ticktin and Shackleton, What is the impact of non-timber forest product (hereafter 2011). The scarcity of studies on these issues for tropical forests NTFP) harvesting on species population dynamics? How does this across the world is an important limitation for their sustainable impact vary with the life history of plants harvested? Are current management, although much of the livelihood of traditional com- rates of exploitation sustainable? These are key questions ad- munities living in such ecosystems is based on NTFPs (Belcher dressed by Peres (2010) about NTFP exploitation. In addition to et al., 2005; Kar and Jacobson, 2012; Zenteno et al., 2013). In spite understanding impacts at the population level, another important of the growing knowledge about the ecological consequences of question without clear answers is related to the impacts of NTFP NTFP exploitation (Ticktin, 2004), overharvesting of NTFP is still a relevant concern for forest management and biological conserva- tion (Ticktin et al., 2002; Peres, 2010; Fernandez et al., 2012). ⇑ Corresponding author. Tel.: +55 19 34294431x233. Overharvesting occurs when the harvest rate of any given nat- E-mail addresses: [email protected] (A.E. Muler), [email protected] ural population exceeds its natural replacement rate (Peres, (D.C. Rother), [email protected] (P.S. Brancalion), [email protected] (R.P. Naves), [email protected] (R.R. Rodrigues), [email protected] (M.A. Pizo). 2010). This process has become one of the most important global 0378-1127/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2013.09.001 118 A.E. Muler et al. / Forest Ecology and Management 324 (2014) 117–125 threats to the maintenance of biodiversity, both for terrestrial and investigated the extraction of leaves and fruits/seeds, so that aquatic ecosystems (Peres, 2010). Unfortunately, the increasing the ecological consequences of palm heart extraction are less global demand for land and food to support the 9 billion people known (Ticktin, 2004). The case study of the exploitation of the estimated to live on Earth by 2050 (Godfray et al., 2010;Smith endangered palm Euterpe edulis in Brazil, locally known as ‘‘pal- et al., 2010; Phalan et al., 2011) does not provide a favorable pros- miteiro’’, provides a valuable template for assessing the possible pect to reduce the pressure on commercially important native spe- consequences of palm heart overharvesting for the dynamics of cies in tropical rainforests. Especially in developing countries, tropical rainforests. This endemic palm species provides the most where most of the population growth, rural poverty, deforestation important NTFP exploited in the Brazilian Atlantic Forest hotspot, and remaining tropical rainforest cover are concentrated, the chal- the palm heart – the apical meristem and developing undifferen- lenge for sustainably exploiting native species within their natural tiated leaves of the palm’s stem (Reis et al., 2000). Given that the habitat is even greater (Kareiva et al., 2007). This holds true not apical meristem is extracted to obtain the palm heart and that only because of the socioeconomic challenge to reduce poverty palmiteiro is a single-stemmed palm that does not re-sprout after and promote economic development without environmental deg- harvesting, palm heart extraction leads to the death of palmiteiro radation, but also due to the inherent ecological complexity of individuals (Reis et al., 2000). According to Peres (2010), ‘‘exploi- tropical rainforests. Whereas many species are more resilient to tation of NTFPs often involves partial or entire removal of indi- exploitation and remain abundant under relatively intense har- viduals from the population, but the extraction method and vesting regimes, others can be driven to local extinction by even whether vital parts are removed usually determine the mortality the lightest exploitation levels (Peres, 2010). Furthermore, if the level in the exploited population’’. Based on this definition, we overexploited species plays an important role for ecosystem func- consider palm heart harvesting as NTFP exploitation, even though tioning, like keystone species for seed dispersers, the reduction in the entire plant is cut. As a result of the predatory exploitation of abundance or extinction of this species can negatively affect the palm heart in the last well-conserved remnants of Atlantic Rain- structure and composition of the ecological community through forest, including protected areas, this species is currently under cascading effects caused by dispersal limitation (Terborgh, 1986; extinction risk (Dransfiled et al., 1988; Galleti and Chivers, Scott Mills et al., 1993). In spite of these risks for biodiversity per- 1955; Galetti and Fernandez, 1998). A recent less-impacting op- sistence, community management of tropical forests has played a tion for the economic use of palmiteiro has been the exploitation relevant role for controlling deforestation in the tropics (Porter- of fruits for producing a southeastern equivalent of the Amazo- bolland et al., 2011). Thus, the exploitation of NTFPs should be bet- nian ‘‘açaí’’ (Euterpe oleracea), the pulp of palm fruits (Brancalion ter investigated in order to obtain the benefits derived from con- et al., 2012), which is currently used for many healthy, nutri- servation-through-use, without the risks of overharvesting and tional perspectives due to its high content of energy, minerals its potential consequences for ecosystem degradation (Fernandez and antioxidants. et al., 2012). Palmiteiro has two important characteristics that can amplify Although there are many case studies in the literature the ecological consequences of its overharvesting for palm heart. reporting overharvesting of timber species in tropical forests, Firstly, it is the most abundant species in the Atlantic rainforest, such as Brazilwood (Caesalpinia echinata – Dean, 1996), East representing nearly 20% of individuals with diameter at breast African blackwood (Dalbergia melanoxylon – Ball, 2004) and height (DBH) > 4.8 cm in conserved areas, with more