“…While a majority of studies cautiously conclude that certification has some positive impacts (Sverdrup-Thygeson et al 2008, Cubbage 2010, Gulbrandsen 2005, Gullison 2003, Newsom and Hewitt 2005, Newsom et al 2006, Nussbaum and Simula 2004, Rametsteiner and Simula 2003, Van Kuijk et al 2009, WWF 2005, most researchers agree that additional research is needed, and that information on the effectiveness of certification standards on the ground is lacking (Auld et al 2008, Ozinga 2004, Peña-Claros et al 2009). Clark and Kozar (2011), authors of a meta-analysis on the impact of forest certification on sustainable forest management practices, conclude: "Despite their existence for more than a decade, little is known about how well forest certification systems achieve their SFM [sustainable forest management] goals.…”