30 research outputs found
Dynamique des populations d'azobé, Lophira alata Banks ex C. F. Gaertn., et implications pour sa gestion durable au Cameroun
L'impact de l'exploitation forestiĂšre sur le renouvellement du stock de bois d'oeuvre reste largement mĂ©connu en Afrique centrale du fait du manque de donnĂ©es sur la dynamique des populations d'arbres exploitĂ©s. C'est en particulier le cas pour l'azobĂ©, Lophira alata, un bois d'oeuvre de grande valeur commerciale. L'objectif de cette Ă©tude est double : quantifier l'effet du type forestier et de l'exploitation sur la croissance de l'azobĂ© et simuler l'Ă©volution du stock exploitable et du taux de reconstitution aprĂšs exploitation. Nous avons effectuĂ© pendant trois ans un suivi annuel de la croissance et de la mortalitĂ© dans trois types forestiers au Cameroun : en forĂȘt sempervirente, en forĂȘt mixte et en forĂȘt semi-caducifoliĂ©e. Le recrute-ment a Ă©tĂ© Ă©tudiĂ© uniquement en forĂȘt mixte, sous deux conditions : en milieu exploitĂ© et non exploitĂ©. Nous avons calibrĂ©, avec ces donnĂ©es, un modĂšle matriciel de Usher. Douze scĂ©narios d'exploitation ont Ă©tĂ© simulĂ©s en faisant varier le diamĂštre minimum d'exploitation de 60, 70 et 80 cm, et l'intensitĂ© de prĂ©lĂšvement des arbres de 100 Ă 40 %. La croissance de l'azobĂ© est influencĂ©e Ă la fois par le type forestier et l'exploitation. Les arbres de forĂȘt sempervirente ont une croissance plus faible jusqu'Ă 50 cm de dia-mĂštre, alors que la croissance maximale prĂ©dite pour ce type forestier est la plus Ă©levĂ©e. L'exploitation a par ailleurs stimulĂ© la croissance. Enfin, l'exploitation de l'azobĂ© ne respecte pas le principe du rendement soutenu : ses taux de croissance Ă long terme varient entre 0,54 et 0,83 %. Pour garantir la durabilitĂ© de son exploitation au Cameroun, une sylviculture dynamisant la croissance des futurs arbres exploitables, ainsi que leur rĂ©gĂ©-nĂ©ration, s'avĂšre indispensable
Standards of conduct and reporting in evidence syntheses that could inform environmental policy and management decisions
Accurate, unbiased and concise synthesis of available evidence following clear methodology and transparent reportâ ing is necessary to support effective environmental policy and management decisions. Without this, less reliable and/ or less objective reviews of evidence could inform decision making, leading to ineffective, resource wasteful interâ ventions with potential for unintended consequences. We evaluated the reliability of over 1000 evidence syntheses (reviews and overviews) published between 2018 and 2020 that provide evidence on the impacts of human activities or effectiveness of interventions relevant to environmental management. The syntheses are drawn from the Colâ laboration for Environmental Evidence Database of Evidence Reviews (CEEDER), an online, freely available evidence service for evidence users that assesses the reliability of evidence syntheses using a series of published criteria. We found that the majority of syntheses have problems with transparency, replicability and potential for bias. Overall, our results suggest that most recently published evidence syntheses are of low reliability to inform decision making. Reviews that followed guidance and reporting standards for evidence synthesis had improved assessment ratings, but there remains substantial variation in the standard of reviews amongst even these. Furthermore, the term âsystemâ atic reviewâ, which implies conformity with a methodological standard, was frequently misused. A major objective of the CEEDER project is to improve the reliability of the global body of environmental evidence reviews. To this end we outline freely available online resources to help improve review conduct and reporting. We call on authors, editors and peer reviewers to use these resources to ensure more reliable syntheses in the future