Dissecting the illegal ivory trade: an analysis of ivory seizures data

Reliable evidence of trends in the illegal ivory trade is important for informing decision making for elephants but it is difficult to obtain due to the covert nature of the trade. The Elephant Trade Information System, a global database of reported seizures of illegal ivory, holds the only extensive information on illicit trade available. However inherent biases in seizure data make it difficult to infer trends; countries differ in their ability to make and report seizures and these differences cannot be directly measured. We developed a new modelling framework to provide quantitative evidence on trends in the illegal ivory trade from seizures data. The framework used Bayesian hierarchical latent variable models to reduce bias in seizures data by identifying proxy variables that describe the variability in seizure and reporting rates between countries and over time. Models produced bias-adjusted smoothed estimates of relative trends in illegal ivory activity for raw and worked ivory in three weight classes. Activity is represented by two indicators describing the number of illegal ivory transactions--Transactions Index--and the total weight of illegal ivory transactions--Weights Index--at global, regional or national levels. Globally, activity was found to be rapidly increasing and at its highest level for 16 years, more than doubling from 2007 to 2011 and tripling from 1998 to 2011. Over 70% of the Transactions Index is from shipments of worked ivory weighing less than 10 kg and the rapid increase since 2007 is mainly due to increased consumption in China. Over 70% of the Weights Index is from shipments of raw ivory weighing at least 100 kg mainly moving from Central and East Africa to Southeast and East Asia. The results tie together recent findings on trends in poaching rates, declining populations and consumption and provide detailed evidence to inform international decision making on elephants

Growth rings in tree species from the Tana river floodplain, Kenya

Growth rings of 19 tree species obtained from the Tana riverine forests in Kenya were studied for potential usefulness in dendrochronology. Among the growth ring characteristics used to qualitatively evaluate the potential usefulness of each species for dendrochronology included: distinctiveness of ring boundaries, ring circuit uniformity, ring wedging and ring sensitivity. Five species were identified as having the most desirable growth ring characteristics and therefore presented the best opportunity to crossdate ring width series among different trees. Crossdating among different trees would lead to the development of tree ring chronologies. These species included Acacia elatior, Acacia robusta, Tamarindus indica and Newtonia hildebrandtii, common on inactive levees occurring toward the edge of the floodplain, and Rinorea elliptica, an understory species found on levees. The timing of growth ring formation and exogenous factors responsible for its formation are yet to be identified. Drought conditions during the low river flow months of August and September are thought responsible for initiation of ring formation as these species grow in a semi-arid region and are thus entirely dependent on ground water.Keywords: cross dating; tree ring analysis; marginal parenchyma; periodicity; wood anatomyJournal of East African Natural History Vol. 95 (2) 2006: pp. 181-21

Biogeographic patterns of forest diversity at mount Kasigau, Kenya

Mount Kasigau, the most northeastern mountain in the Eastern Arc, rises steeply from arid plains to a moist summit at 1641 m. This paper examines the diversitycontributions of this afromontane setting by compiling a chorological analysis of tree species richness, measuring ecological differences among forest community types, and interpreting physical-environmental and human-historical factors that influence diversity patterns. Between 2002 and 2006, stem densities and basal areas of woody plants >10 cm dbh were measured in 55 (0.1 ha) plots placed at different elevations. The study reports 140 species, 46 were measured in only one plot, and affinities for 75 species to the Somalia-Masai (43%), Afromontane (29%), and Zanzibar- Inhambane (Coastal, 28%) floristic regions. Cluster and Indicator Species Analyses identified eight community types. Mount Kasigau uniquely conserves much forest cover and a diversity of woody plant species below evergreen forest at 1000 m. Ordination, using Nonmetric Multidimensional Scaling (NMDS), resulted in a threedimensional solution that explained 47.9% of the variation among plots. Axis 2 showed the strongest relationship with elevation (R2= 0.523), but lower montane community types also vary by slope form, slope aspect, and past human activities. We show how this biogeographical analysis of diversity patterns at Mount Kasigau can guide local management and support important opportunities for montane forest conservation in East Africa.Keywords: afromontane; Eastern Arc Mountains; montane vegetation, plant diversity,tropical forest ecolog