• Energy Research

AbstractNon-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance indicating that human-mediated transport may serve as a pathway of the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

Abstract In Burkina Faso, the leaf beetle Aphthona whitfieldi is the main insect pest of the biofuel plant Jatropha curcas. The beetle affects plant growth and seed yield, but the impact on yield has never been properly quantified. This study was conducted on-station and on-farm in the district of Léo, southern Burkina Faso, in 2015. It aimed at evaluating the yield losses that A. whitfieldi inflicts to J. curcas. The first experiment used 25 caged trees in their first year of fruit production, on which various amounts of beetles were released. When 200 beetles were released, the defoliation level reached 55% and caused 61% of yield loss. Releases of 400 or more beetles caused a defoliation level of at least 74% and seed losses of 98%. On-farm observations were made on attack levels and seed yields in three different types of plantations, i.e. pure plantations, plantations intercropped with food crops and hedges. These observations showed that defoliation levels over 50% were common in the three types of plantations, resulting in very low yields. This study shows the importance of beetle damage in the cultivation of J. curcas. This is likely one of the reasons for the very low yields, which, among other causes, led to the abandonment of J. curcas plantations in the region.

We tested whether two basic thermal requirements for insect development, lower developmental thresholds, i.e. temperatures at which development ceases, and sums of effective temperatures, i.e. numbers of day degrees above the lower developmental thresholds necessary to complete development, differ among insect species that proved to be successful invaders in regions outside their native range and those that did not. Focusing on species traits underlying invasiveness that are related to temperature provides insights into the mechanisms of insect invasions. The screening of thermal requirements thus could improve risk-assessment schemes by incorporating these traits in predictions of potentially invasive insect species. We compared 100 pairs of taxonomically-related species originating from the same continent, one invasive and the other not reported as invasive. Invasive species have higher lower developmental thresholds than those never recorded outside their native ranges. Invasive species also have a lower sum of effective temperatures, though not significantly. However, the differences between invasive and non-invasive species in the two physiological measures were significantly inversely correlated. This result suggests that many species are currently prevented from invading by low temperatures in some parts of the world. Those species that will overcome current climatic constraints in regions outside their native distribution due to climate change could become even more serious future invaders than present-day species, due to their potentially faster development.

Abstract The biofuel crop Jatropha curcas has been promoted in developing countries as a means of improving the livelihoods of rural populations. In Mexico, despite the initially assumed economic, environmental, and social benefits of the crop, many farmers have abandoned jatropha cultivation. Here, we analyse the factors that influence farmers' decision to abandon jatropha cultivation by using a generalized linear modelling approach in combination with qualitative research methods. The deterioration in perception of jatropha profitability, the non-payment of expected subsidies and the wealth position of the household played a major role in determining abandonment. The perception of pest and disease damage, although stated by farmers as the second most frequent reason to disadopt, was not correlated with this decision in the generalized linear model. This research might help energy policy makers in identifying key elements to prevent failure of promotion programmes. The result of this study also may be useful for an international audience to reflect on the appropriateness of promoting a new crop at the farmer level before realistically evaluating the economic viability of its cultivation.

While the concept of insect based feeds (IBFs) promises great potential, especially in developing countries, the sustainability performance of IBF production remains widely underexplored. Drawing on experimental data from rearing trials in West Africa, three different insect production systems were modelled ex-ante. The generic models served as a basis to analyse and compare the process performances of different IBF production systems using Musca domestica and Hermetia illucens reared on different substrates. The results show that the input efficiency in the production of IBF is largely determined by the quality of rearing substrates, the larval development time and the employed inoculation practises, i.e., the method by which eggs or larvae are added to rearing substrates. The H. illucens system ranked highest for conversion efficiency (substrate input per IBF output), but showed substantially higher inputs in labour, fossil energy and output of wastewater. M. domestica systems operated at lower conversion efficiencies, which resulted in higher outputs of residue substrates, together with higher emissions, land requirements, built infrastructure and water. By offering full disclosure of generic inventory data, this study provides data and inspiration for prospect research and development activities and offers a reference to future life cycle assessments (LCAs) on IBF.