Andrew R. Marshall

Positive biodiversity-productivity relationship predominant in global forests.

Global biodiversity and productivity The relationship between biodiversity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from >770,000 sample plots in 44 countries. A positive and consistent relationship can be discerned between tree diversity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in biodiversity leads to a 3% loss in productivity. This means that the economic value of maintaining biodiversity for the sake of global forest productivity is more than fivefold greater than global conservation costs. Science, this issue p. 196 Global forest inventory records suggest that biodiversity loss would result in a decline in forest productivity worldwide. INTRODUCTION The biodiversity-productivity relationship (BPR; the effect of biodiversity on ecosystem productivity) is foundational to our understanding of the global extinction crisis and its impacts on the functioning of natural ecosystems. The BPR has been a prominent research topic within ecology in recent decades, but it is only recently that we have begun to develop a global perspective. RATIONALE Forests are the most important global repositories of terrestrial biodiversity, but deforestation, forest degradation, climate change, and other factors are threatening approximately one half of tree species worldwide. Although there have been substantial efforts to strengthen the preservation and sustainable use of forest biodiversity throughout the globe, the consequences of this diversity loss pose a major uncertainty for ongoing international forest management and conservation efforts. The forest BPR represents a critical missing link for accurate valuation of global biodiversity and successful integration of biological conservation and socioeconomic development. Until now, there have been limited tree-based diversity experiments, and the forest BPR has only been explored within regional-scale observational studies. Thus, the strength and spatial variability of this relationship remains unexplored at a global scale. RESULTS We explored the effect of tree species richness on tree volume productivity at the global scale using repeated forest inventories from 777,126 permanent sample plots in 44 countries containing more than 30 million trees from 8737 species spanning most of the global terrestrial biomes. Our findings reveal a consistent positive concave-down effect of biodiversity on forest productivity across the world, showing that a continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The BPR shows considerable geospatial variation across the world. The same percentage of biodiversity loss would lead to a greater relative (that is, percentage) productivity decline in the boreal forests of North America, Northeastern Europe, Central Siberia, East Asia, and scattered regions of South-central Africa and South-central Asia. In the Amazon, West and Southeastern Africa, Southern China, Myanmar, Nepal, and the Malay Archipelago, however, the same percentage of biodiversity loss would lead to greater absolute productivity decline. CONCLUSION Our findings highlight the negative effect of biodiversity loss on forest productivity and the potential benefits from the transition of monocultures to mixed-species stands in forestry practices. The BPR we discover across forest ecosystems worldwide corresponds well with recent theoretical advances, as well as with experimental and observational studies on forest and nonforest ecosystems. On the basis of this relationship, the ongoing species loss in forest ecosystems worldwide could substantially reduce forest productivity and thereby forest carbon absorption rate to compromise the global forest carbon sink. We further estimate that the economic value of biodiversity in maintaining commercial forest productivity alone is

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

166 billion to

Selection of line-transect methods for estimating the density of group-living animals: lessons from the primates.

490 billion per year. Although representing only a small percentage of the total value of biodiversity, this value is two to six times as much as it would cost to effectively implement conservation globally. These results highlight the necessity to reassess biodiversity valuation and the potential benefits of integrating and promoting biological conservation in forest resource management and forestry practices worldwide. Global effect of tree species diversity on forest productivity. Ground-sourced data from 777,126 global forest biodiversity permanent sample plots (dark blue dots, left), which cover a substantial portion of the global forest extent (white), reveal a consistent positive and concave-down biodiversity-productivity relationship across forests worldwide (red line with pink bands representing 95% confidence interval, right). The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US

Delimiting tropical mountain ecoregions for conservation

166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.

Monkey abundance and social structure in two high-elevation forest reserves in the Udzungwa mountains of Tanzania

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.

Demographic variation among Udzungwa red colobus in relation to gross ecological and sociological parameters

We review the four major contemporary methods for estimating density of group‐living animals from line‐transect sampling: perpendicular modelling of group centers, perpendicular modelling of center of measurable individuals, strip transects and animal–observer distance. The efficacy of each method is evaluated to produce a simple selection guide. We review the literature and use field data from the Udzungwa Mountains, Tanzania. The review is relevant to all group‐living animals; however, examples are drawn from the primates. Perpendicular methods have better mathematical justification than non‐perpendicular methods. For perpendicular methods using detection function models, it is preferable to measure group location using center of measurable individuals, as group centers are hard to estimate. The assumptions of detection function models are often broken in poor visibility habitats or with unhabituated animals. Alternatively strip transects may be used where there are reliable data on group spread and/or visibility. Strip transects are also the most practical, along with the animal–observer method; however, the latter lacks mathematical justification. We conclude that there are arguments for continued use of all four methods. In certain situations the use of raw encounter rates may also be considered. The appropriate method is determined by minimizing bias and considering time, resources and field conditions. Am. J. Primatol. 70:452–462, 2008.

Measuring, modeling and mapping ecosystem services in the Eastern Arc Mountains of Tanzania

��������� � �� ���������� SUMMARY Ecological regions aggregate habitats with similar biophysical characteristics within well-defined boundaries, providing spatially consistent platforms for monitoring, managing and forecasting the health of interrelated ecosystems. A major obstacle to the implementation of this approach is imprecise and inconsistent boundary placement. For globally important mountain regions such as the Eastern Arc (Tanzania and Kenya), where qualitative definitions of biophysical affinity are well established, rulebased methods for landform classification provide a straightforward solution to ambiguities in region extent. The method presented in this paper encompasses the majority of both contemporary and estimated preclearance forest cover within strict topographical limits. Many of the species here tentatively considered ‘near-endemic’ could be reclassified as strictly endemic according to the derived boundaries. LandScan and census data show population density inside the ecoregion to be higher than in rural lowlands, and lowland settlement to be most probable within 30 km. This definition should help to align landscape scale conservation strategies in the Eastern Arc and promote new research in areas of predicted, but as yet undocumented, biological importance. Similar methods could work well in other regions where mountain extent is poorly resolved. Spatial data accompany the online version of this article.

Estimating the abundance of forest antelopes by line transect techniques: a case from the Udzungwa Mountains of Tanzania

The effects of human activity on population and social structure are a pantropical concern for primate conservation. We compare census data and social group counts from two forests in the Udzungwa Mountains, Tanzania. The main aim is to relate differences within and between the forests to current theory on the effect of human disturbance on primate abundance and group size. The survey reveals the presence of the restricted-range red colobus, Procolobus gordonorum, in New Dabaga/Ulangambi Forest Reserve (NDUFR). The primate community of NDUFR is impoverished compared to that in Ndundulu forest. Red colobus and black-and-white colobus (Colobus angolensis palliatus) abundance and group size are lowest in NDUFR. Fission-fusion of red colobus social groups may be occurring in previously logged areas of both forests. Our observations are consistent with current theory on the effect of habitat degradation and hunting on primates, but the relative effects of the 2 factors could not be differentiated. We pooled the results with previous data to show that abundance of red colobus in the Udzungwa Mountains is lowest at high elevations. Low red colobus group sizes appear to be related to human activity rather than elevation. Black-and-white colobus and Sykes monkeys (Cercopithecus mitis) show no relationship with elevation. Future studies will require more detailed information on vegetation, diet and ranging patterns to interpret fully intraspecific variation in population demography and social structure in the Udzungwa Mountains.

Contrasting effects of defaunation on aboveground carbon storage across the global tropics

We evaluated variation in group size and composition of Udzungwa red colobus (Procolobus gordonorum) in relation to gross-habitat and sociological parameters. The endangered species is endemic to the Udzungwa Mountains and nearby forests in the Kilombero Valley of south-central Tanzania. We counted 63 groups in 10 forests, ranging in altitude from 250 to 1,800 m. Group size ranged from 7 to 83 (x = 36.3) individuals and adult sex ratios (females/male) ranged from 1.5 to 7.3 (x = 3.5), excluding solitary individuals. Group size was influenced by several habitat parameters, including tree density, degree of deciduousness, and forest size. Groups were largest in large blocks of mature, moist, mixed evergreen and semideciduous forests, but group size is not correlated with altitude. Groups in a highly degraded forest appeared to have fission-fusion societies. The effect of habitat quality on age-sex composition of groups was most apparent in natality and less so in survivorship of adult females and juveniles. The number of adult males in groups accounted for 50% of the variance in group size and 34–39% of the variance in numbers of adult females in groups. Habitat quality affects natality more than demographic parameters do. Groups with a low proportion of adult females had greater juvenile survivorship, perhaps because of lower food competition between these two classes. We proffer hypotheses based on our study and previous intertaxonal comparisons to explain cause and effect relationships between habitat quality and demography. Finally, our study demonstrates the importance of large blocks of old-growth forest to the conservation of Udzungwa red colobus, and we make recommendations for conservation and research.

Relative densities of mammals in response to different levels of bushmeat hunting in the Udzungwa Mountains, Tanzania.

In light of the significance that ecosystem service research is likely to play in linking conservation activities and human welfare, systematic approaches to measuring, modeling and mapping ecosystem services (and their value to society) are sorely needed. In this paper we outline one such approach, which we developed in order to understand the links between the functioning of the ecosystems of Tanzania’s Eastern Arc Mountains and their impact on human welfare at local, regional and global scales. The essence of our approach is the creation of a series of maps created using field-based or remotely sourced data, data-driven models, and socio-economic scenarios coupled with rule-based assumptions. Here we describe the construction of this spatial information and how it can help to shed light on the complex relationships between ecological and social systems. There are obvious difficulties in operationalizing this approach, but by highlighting those which we have encountered in our own case-study work, we have also been able to suggest some routes to overcoming these impediments.