Jon C. Lovett

Increasing carbon storage in intact African tropical forests

The response of terrestrial vegetation to a globally changing environment is central to predictions of future levels of atmospheric carbon dioxide. The role of tropical forests is critical because they are carbon-dense and highly productive. Inventory plots across Amazonia show that old-growth forests have increased in carbon storage over recent decades, but the response of one-third of the world’s tropical forests in Africa is largely unknown owing to an absence of spatially extensive observation networks. Here we report data from a ten-country network of long-term monitoring plots in African tropical forests. We find that across 79 plots (163 ha) above-ground carbon storage in live trees increased by 0.63 Mg C ha-1 yr-1 between 1968 and 2007 (95% confidence interval (CI), 0.22–0.94; mean interval, 1987–96). Extrapolation to unmeasured forest components (live roots, small trees, necromass) and scaling to the continent implies a total increase in carbon storage in African tropical forest trees of 0.34 Pg C yr-1 (CI, 0.15–0.43). These reported changes in carbon storage are similar to those reported for Amazonian forests per unit area, providing evidence that increasing carbon storage in old-growth forests is a pan-tropical phenomenon. Indeed, combining all standardized inventory data from this study and from tropical America and Asia together yields a comparable figure of 0.49 Mg C ha-1 yr-1 (n = 156; 562 ha; CI, 0.29–0.66; mean interval, 1987–97). This indicates a carbon sink of 1.3 Pg C yr-1 (CI, 0.8–1.6) across all tropical forests during recent decades. Taxon-specific analyses of African inventory and other data suggest that widespread changes in resource availability, such as increasing atmospheric carbon dioxide concentrations, may be the cause of the increase in carbon stocks, as some theory and models predict.

Geographical patterns of old and young species in African forest biota: the significance of specific montane areas as evolutionary centres

A widely accepted paradigm for speciation in tropical forests, the refuge theory, requires periodic habitat fragmentation driven by global climatic fluctuations to provide conditions for allopatric speciation. This implies that comparative species richness in refugia is due to loss of diverse communities in areas affected by climatic cycles. In this study we compare distribution patterns of bird and plant taxa which we consider to be of either deep phylogenetic lineages or recent radiations. It is demonstrated that lowland areas which have been postulated as Pleistocene refugia are dominated by species which represent lineages of pre-Pleistocene age. Since variations in species richness within these forest tracts reflect currently apparent environmental variables which might be considered to determine carrying capacity, we do not need to postulate that richness is the result of changes in forest cover in the past. Recently diversified taxa of plants and birds are found mainly at the periphery of the main rain forest blocks and in habitat islands outside them. Here, peak concentrations of young restricted-range species are often congruent with clusters of old and biogeographically relictual species. It is suggested that this reflects special intrinsic environmental properties of these areas, in the form of long-term environmental stability caused mainly by persistent orographic rain or mist. In this case, richness is not necessarily due to extinction outside these areas. Stability not only enables survival of relictual taxa, but also promotes morphological differentiation of radiating taxa, leading to aggregates of taxa of restricted distribution.

Drought–mortality relationships for tropical forests

*The rich ecology of tropical forests is intimately tied to their moisture status. Multi-site syntheses can provide a macro-scale view of these linkages and their susceptibility to changing climates. Here, we report pan-tropical and regional-scale analyses of tree vulnerability to drought. *We assembled available data on tropical forest tree stem mortality before, during, and after recent drought events, from 119 monitoring plots in 10 countries concentrated in Amazonia and Borneo. *In most sites, larger trees are disproportionately at risk. At least within Amazonia, low wood density trees are also at greater risk of drought-associated mortality, independent of size. For comparable drought intensities, trees in Borneo are more vulnerable than trees in the Amazon. There is some evidence for lagged impacts of drought, with mortality rates remaining elevated 2 yr after the meteorological event is over. *These findings indicate that repeated droughts would shift the functional composition of tropical forests toward smaller, denser-wooded trees. At very high drought intensities, the linear relationship between tree mortality and moisture stress apparently breaks down, suggesting the existence of moisture stress thresholds beyond which some tropical forests would suffer catastrophic tree mortality.

Biodiesel as feasible petrol fuel replacement: a multidisciplinary overview

Biodiesel is a sustainable, non-toxic, biodegradable diesel fuel substitute that can be employed in current diesel car infrastructure without major modifications in the engines. It has a significant added value compared to petroleum-based diesel, reflected in a series of improved properties including fewer carcinogenic particulate matter emissions, increased lubricity and biodegradability as well as ease of handling, transport and storage. Nevertheless, it is essential that the biodiesel life-cycle is environmentally sustainable, economically viable, and socially acceptable; views that can only be properly analysed by means of a multi-angle approach. In this contribution, we aim to provide a multidisciplinary perspective on key issues for the successful implementation of biodiesel as a petrol fuel replacement including green chemistry methods to improve production and quality, the use of energy crops and feedstocks for second-generation biodiesel as well as socio-economic studies and the importance of governmental regulatory issues.

Mapping More of Terrestrial Biodiversity for Global Conservation Assessment

Abstract Global conservation assessments require information on the distribution of biodiversity across the planet. Yet this information is often mapped at a very coarse spatial resolution relative to the scale of most land-use and management decisions. Furthermore, such mapping tends to focus selectively on better-known elements of biodiversity (e.g., vertebrates). We introduce a new approach to describing and mapping the global distribution of terrestrial biodiversity that may help to alleviate these problems. This approach focuses on estimating spatial pattern in emergent properties of biodiversity (richness and compositional turnover) rather than distributions of individual species, making it well suited to lesser-known, yet highly diverse, biological groups. We have developed a global biodiversity model linking these properties to mapped ecoregions and fine-scale environmental surfaces. The model is being calibrated progressively using extensive biological data sets for a wide variety of taxa. We also describe an analytical approach to applying our model in global conservation assessments, illustrated with a preliminary analysis of the representativeness of the worlds protected-area system. Our approach is intended to complement, not compete with, assessments based on individual species of particular conservation concern.

Biodiversity and environmental stability

Although levels of biological diversity may seem to be equivalent in different areas, diversity is created and maintained by a range of different ]processes: overlap of habitat on gradients; a dynamic mosaic of communities; and accumulation and evolution of taxa in extremely stable areas. These different communities will respond in very different ways to disturbance. The most fragile are those whose component taxa are genetically adapted to the stability of a predictable environment. These areas are often under pressure from local rural populations and require intensive local conservation management actions. In other areas, where diversity is adapted to dynamism, communities are more resilient to disturbance and conservation can be best effected by policy instruments.

Getting ready for REDD+ in Tanzania: a case study of progress and challenges

The proposed mechanism for Reducing Emis- sions from Deforestation and Degradation (REDD+) offers significant potential for conserving forests to reduce negative impacts of climate change. Tanzania is one of nine pilot countries for the United Nations REDD Pro- gramme, receives significant funding from the Norwegian, Finnish and German governments and is a participant in the World Banks Forest Carbon Partnership Facility. In combination, these interventions aim to mitigate green- house gas emissions, provide an income to rural commu- nities and conserve biodiversity. The establishment of the UN-REDD Programme in Tanzania illustrates real-world challenges in a developing country. These include currently inadequate baseline forestry data sets (needed to calculate reference emission levels), inadequate government capacity and insufficient experience of implementing REDD+-type measures at operational levels. Additionally, for REDD+ to succeed, current users of forest resources must adopt new practices, including the equitable sharing of benefits that accrue from REDD+ implementation. These challenges are being addressed by combined donor support to im- plement a national forest inventory, remote sensing of forest cover, enhanced capacity for measuring, reporting and verification, and pilot projects to test REDD+ imple- mentation linked to the existing Participatory Forest Man- agement Programme. Our conclusion is that even in a country with considerable donor support, progressive forest policies, laws and regulations, an extensive network of managed forests and increasingly developed locally-based forest management approaches, implementing REDD+ pre- sents many challenges. These are being met by coordinated, genuine partnerships between government, non-government and community-based agencies.

Local perceptions of risk to livelihood in semi-arid Tanzania

This paper examines variation in local perceptions of risk in semi-arid Tanzania, identifying factors that influence local perceptions of problems and testing the feasibility of risk mapping as a technique. Twelve villages in six districts were visited between February and April 2001. Villagers were asked about their worries and concerns in providing for themselves and their families using a risk questionnaire. The responses were grouped into 21 categories of problem and incidence and severity indices were calculated for each category. Most problems were associated with the availability of natural resources on which livelihoods depend but others related to human and social capital assets. In addition to environmental factors, livelihood strategy and gender both influenced peoples perceptions of risk. Problems of irrigation and weather, for example, were important for agricultural communities while problems relating to livestock diseases, access to land and hunger were more important in pastoral communities. The risks cited by men and women generally reflected their traditional roles in society. Very broadly, the risks associated with natural capital tended to be seen as higher by men while women mentioned more problems relating to human and social capital. However, this was not always the case. Problems linked to finance, traditionally the concern of men, were ranked similarly by men and women. In projects designed to facilitate community management and control over common pool resources, the identification of common interests is particularly important. Risk mapping can provide a cost-effective way of gaining insights to help improve research design and to inform policy development.

Elevational and latitudinal changes in tree associations and diversity in the Eastern Arc mountains of Tanzania

A total of 200 variable-area plots covering 20.3 ha containing 4000 trees with a basal area of 921.4 m2 were assessed over a combined elevational range of 410-2180 m in the moist forests of three Tanzanian Eastern Arc mountains: West Usambara, Nguru and Udzungwa. Plot data were ordinated on the basis of species presence/absence, frequency and basal area. Axis 1 of ordinations based on species presence/absence are correlated with elevation. Axis 1 of the frequency-weighted ordination was correlated with elevation in the Nguru and Udzungwa moun- tains, but plots from the West Usambara showed a rainfall-related discontinuity. Axis 1 of the West Usambara basal area-weighted ordination showed evidence of long-term dynamics of Ocotea usambarensis and in the Udzungwa mountains was determined by presence of Parinari excelsa. Plot diversity was not correlated with elevation or latitude, but was lower in disturbed, low rainfall or more seasonal forest. Stem density was positively correlated with elevation and was greater on ridge tops than valley sides and valley bottoms.

Institutions and collective action: Does heterogeneity matter in community-based resource management?

Abstract This article examines the relationship between local level heterogeneity and the likelihood of successful collective action in community-based forest management in Nepal. Economic and social heterogeneity are discussed and their effects on local level collective action considered. The study develops simple measures of inequality for key variables, and shows that there is no clear-cut impact of group heterogeneity on collective action. Forest user groups can create institutions for resource management according to their local context in order to avoid management problems created by inequalities among resource users. Perhaps the most important result is that the effects of heterogeneity can be highly variable, and the recommendation is that systems of governance need to be flexible to allow adaptation of management regimes to local conditions.