Since the first edition of the State of the Forest (SOF), the state and conservation of biodiversity have been a continuing concern. Every subsequent edition has reviewed the threats to the fauna and flora of the subregion. In 2010, the subject was presented in a chapter entitled “Biodiversity in the forests of Central Africa : panorama of knowledge, principal challenges and conservation measures” (Billand, 2012). By devoting a new chapter to this subject, the SOF 2013 reaffirms the importance of biodiversity and the protection of species for the sustainable development of the forests of Central Africa. The present chapter is not a monograph of the current situation; it makes no claim to be an exhaustive treatment of the biological diversity of Central Africa. Rather it follows the panorama drawn earlier while highlighting additional knowledge acquired and the tools available to follow the changes of the biodiversity and to facilitate its management. It also addresses some topical questions and recent experiences with the management / conservation of animal and plant biodiversity. The first part of the chapter, which is particularly innovative, describes the available methods for estimating biodiversity in the forests of Central Africa. The first section concerns the large mammals, including most of the emblematic species; it then presents methodologies for evaluating plant diversity. The second part presents the status of a number of emblematic species. It provides the most recent information on the critical status of elephant and great ape populations. After reviewing the state of knowledge of plant diversity, this section also describes the problems of invasive species through examples of the small fire-ant in Gabon and Cameroon, and the invasive plants in Sao Tomé. Surprisingly, this threat to the ecosystems of Central Africa has so far been given little attention by conservationists.Several biodiversity tools and approaches are presented in the third and fourth parts. Attention is focused, inter alia, on the fundamental role of herbaria for the knowledge, conservation and management of plant biodiversity. A preliminary review of the trans-boundary protected area initiatives is presented, following the conservation measures described in SOF 2010. Lastly, Central Africa continues to be confronted with the extensive and indeed resurgent phenomenon of poaching and trafficking in animal species. Considerable attention is therefore given to the challenge to combat poaching. This question is addressed transversally in the last two chapters, which highlight concerted multiple action programs being developed in the region, including cross-border management