Changes in ant communities along an age gradient of cocoa cultivation in the Oumé region,central Côte d'Ivoire

We identified the extent to which ant diversity occurs despite conversion of forests into cocoa plantations by examining the communities across four age classes of plantations (classes I–IV with increasing age from 0–5 to 21–40 years) and in their original forests. An extensive sampling protocol consisting of pitfall trapping, leaf litter sampling, soil sampling and hand sampling was used to characterize ant species richness and composition in three replicates of each age class and in the remaining forest patches. A total of one hundred ant species was found in all habitats combined. While the forest was the richest habitat (73 species), species richness in the different plantation age classes varied as follows (sorted in descending order): class IV (69 species) > class III (57 species) > class I (52 species) > class II (43 species). Age gradient was thus significantly positively correlated with mean species richness and with the relative abundance of some subfamilies. The species composition differed greatly between some plantation age classes and the forest. The two youngest cocoa age classes (I and II) were most dissimilar to the forest. In contrast, forest ants were well represented in the old cocoa age classes (III and IV). Three functional guilds (generalist predators, specialist predators and territorially dominant arboreal species) were in their relative abundance significantly correlated to the age gradient. Overall, cocoa cultivations retaining a floristically diverse and structurally complex forest structure are a suitable management system for the conservation of ant species of the formerly forested habitats.     

The influence of time,soil characteristics,and land‐use history on soil phosphorus legacies: a global meta‐analysis

Agriculturally driven changes in soil phosphorus (P) are known to have persistent effects on local ecosystem structure and function, but regional patterns of soil P recovery following cessation of agriculture are less well understood. We synthesized data from 94 published studies to assess evidence of these land‐use legacies throughout the world by comparing soil labile and total P content in abandoned agricultural areas to that of reference ecosystems or sites remaining in agriculture. Our meta‐analysis shows that soil P content was typically elevated after abandonment compared to reference levels, but reduced compared to soils that remained under agriculture. There were more pronounced differences in the legacies of past agriculture on soil P across regions than between the types of land use practiced prior to abandonment (cropland, pasture, or forage grassland). However, consistent patterns of soil P enrichment or depletion according to soil order and types of post‐agricultural vegetation suggest that these factors may mediate agricultural legacies on soil P. We also used mixed effects models to examine the role of multiple variables on soil P recovery following agriculture. Time since cessation of agriculture was highly influential on soil P legacies, with clear reductions in the degree of labile and total P enrichment relative to reference ecosystems over time. Soil characteristics (clay content and pH) were strongly related to changes in labile P compared to reference sites, but these were relatively unimportant for total P. The duration of past agricultural use and climate were weakly related to changes in total P only. Our finding of reductions in the degree of soil P alteration over time relative to reference conditions reveals the potential to mitigate these land‐use legacies in some soils. Better ability to predict dynamics of soil nutrient recovery after termination of agricultural use is essential to ecosystem management following land‐use change.     

Transpirational Water Loss in Invaded and Restored Semiarid Riparian Forests

The invasive tree, Tamarix sp., was introduced to the United States in the 1800s to stabilize stream banks. The riparian ecosystem adjacent to the middle Rio Grande River in central New Mexico consists of mature cottonwood (Populus fremontii) gallery forests with a dense Tamarix understory. We hypothesized that Populus would compensate for reduced competition by increasing its water consumption in restored riparian plots following selective Tamarix removal, resulting in similar transpiration (T) among stands. The northern study site included a Populus stand invaded by Tamarix (INV_N) and a restored Populus‐only stand (RES_N), as did a southern site (INV_S and RES_S) approximately 80 miles south. At each site, 20 × 20–m plots were established where up to 16 stems were monitored throughout the 2004 growing season using thermal dissipation sapflow sensors. Populus sapflux rates were greater in restored stands, suggesting those trees compensated for understory removal by using more water. Sapflow was scaled to estimate stand‐level T based on a quantitative assessment of sapwood basal area (A_sw) by species. Although exotic species represented 85 and 91% of the total stems in the invaded stands, it amounted to only 3% (INV_S) and 4% (INV_N) of the total A_sw, contributing proportionately less to T compared to Populus. Our results indicate that removing Tamarix from the Populus understory in this riparian forest had a minimal impact on stand water balance. Riparian restoration of the type discussed herein should focus primarily on enhancing riparian health rather than generating water.     

Fast Carbon Footprinting for Large Product Portfolios

Publicly Available Specification 2050‐2011 (PAS 2050), the Green House Gas Product Protocol (GHGPP) standard and forthcoming guideline 14067 from the International Organization for Standardization (ISO) have helped to propel carbon footprinting from a subdiscipline of life cycle assessment (LCA) to the mainstream. However, application of carbon footprinting to large portfolios of many distinct products and services is immensely resource intensive. Even if achieved, it often fails to inform company‐wide carbon reduction strategies because footprint data are disjointed or don't cover the whole portfolio. We introduce a novel approach to generate standard‐compliant product carbon footprints (CFs) for companies with large portfolios at a fraction of previously required time and expertise. The approach was developed and validated on an LCA dataset covering 1,137 individual products from a global packaged consumer goods company. Three novel techniques work in concert in a single approach that enables practitioners to calculate thousands of footprints virtually simultaneously: (i) a uniform data structure enables footprinting all products and services by looping the same algorithm; (ii) concurrent uncertainty analysis guides practitioners to gradually improve the accuracy of only those data that materially impact the results; and (iii) a predictive model generates estimated emission factors (EFs) for materials, thereby eliminating the manual mapping of a product or service's inventory to EF databases. These autogenerated EFs enable non‐LCA experts to calculate approximate CFs and alleviate resource constraints for companies embarking on large‐scale product carbon footprinting. We discuss implementation roadmaps for companies, including further road‐testing required to evaluate the effectiveness of the approach for other product portfolios, limitations, and future improvements of the fast footprinting methodology.     

Response to Wiedmann

This commentary is prompted by Thomas Wiedmann's “Defining (Urban) Producer and Consumer Sinks” published in this issue. In his article, Wiedmann presents a new framework for categorizing carbon sinks by borrowing practices from carbon emissions accounting and, essentially, proposing a “carbon sink footprint” model for urban inventories. While this is a valuable new concept, we argue that it is difficult to apply accurately given current knowledge and practices in urban life cycle assessment. Instead, a direct versus embodied classification based on where the sequestration service exists, not where the sink is located, is more useful from the perspective of municipal control and influence over creating and managing carbon sinks. This is ultimately important for the development of urban climate change mitigation measures.     

Estimation of Copper In‐use Stocks in Nanjing,China

Copper (Cu) is an essential but supply‐restricted resource in China. Characterization of in‐use stocks can provide useful instruction for the future recycling of copper. This article attempts to estimate copper in‐use stocks in a Chinese city. To this purpose, an extensive bottom‐up estimate of copper stocks in use in Nanjing in the year 2009 was conducted. The results are a total stock estimate of 295 gigagrams (Gg) of copper or 46.9 kilograms (kg) of copper per capita for 2009. Infrastructure, equipment, and buildings contain 42.0%, 26.1%, and 28.1% of the total stock, respectively, indicating that these three categories are principal potential reservoirs of a secondary copper resource. The copper in transportation amounts to only about 3.7% of the total amount. The per capita stock was compared with similar studies carried out in other regions of the world, and the results show that the Nanjing level is significantly lower than developed countries. On the whole, our results show that electric power transmission and distribution systems, buildings, household durables, and industrial equipment are the four largest potential reservoirs of copper scrap.     

Plantlet recruitment is the key demographic transition in invasion by Kalanchoe daigremontiana

Biological invasions have a great impact on biodiversity and ecosystem functioning worldwide. Kalanchoe daigremontiana is a noxious invasive plant in arid zones. Besides being toxic for domestic animals and wildlife, this species inhibits the growth of native plants. Its rapid proliferation in Cerro Saroche National Park (Venezuela) is of great concern because this area hosts several species endemic to the scarce arid zones in the Caribbean. The traits of K. daigremontiana that contribute to its invasive success are unknown. Based on empirical data, we derived a stage structured, stochastic and density-dependent model, to identify characteristics relevant for its establishment. Sensitivity analyses revealed that the establishment of K. daigremontiana depends exclusively on plantlet recruitment. Because asexual plantlets reproduce in less than 1 year populations are able to increase rapidly during the initial phases of invasion, when extinction risks are higher. Sexual seedlings, on the contrary, require a minimum of 3 years to reproduce. As a result, seedling recruitment contributes little to the transient dynamics of the population and therefore cannot warrant the successful establishment of the species. Simulations of various management strategies show that eradication through plant removal may only be achieved if harvest begins shortly after introduction. If a rapid response is not possible, reducing the survival and growth rates of plantlets through biological control is an alternative option. Thus, a strict control of dispersal of plantlets by humans and a continuous monitoring of new invasions should be the first priority for reducing further impact on native species.     

Optimal surveillance and eradication of invasive species in heterogeneous landscapes

Cost-effective surveillance strategies are needed for efficient responses to biological invasions and must account for the trade-offs between surveillance effort and management costs. Less surveillance may allow greater population growth and spread prior to detection, thereby increasing the costs of damages and control. In addition, surveillance strategies are usually applied in environments under continual invasion pressure where the number, size and location of established populations are unknown prior to detection. We develop a novel modeling framework that accounts for these features of the decision and invasion environment and determines the long term sampling effort that minimises the total expected costs of new invasions. The optimal solution depends on population establishment and growth rates, sample sensitivity, and sample, eradication, and damage costs. We demonstrate how to optimise surveillance systems under budgetary constraints and find that accounting for spatial heterogeneity in sampling costs and establishment rates can greatly reduce management costs.     

The value of coordinated management of interacting ecosystem services

Coordinating decisions and actions among interacting sectors is a critical component of ecosystem-based management, but uncertainty about coordinated management's effects is compromising its perceived value and use. We constructed an analytical framework for explicitly calculating how coordination affects management decisions, ecosystem state and the provision of ecosystem services in relation to ecosystem dynamics and socio-economic objectives. The central insight is that the appropriate comparison strategy to optimal coordinated management is optimal uncoordinated management, which can be identified at the game theoretic Nash equilibrium. Using this insight we can calculate coordination's effects in relation to uncoordinated management and other reference scenarios. To illustrate how this framework can help identify ecosystem and socio-economic conditions under which coordination is most influential and valuable, we applied it to a heuristic case study and a simulation model for the California Current Marine Ecosystem. Results indicate that coordinated management can more than double an ecosystem's societal value, especially when sectors can effectively manipulate resources that interact strongly. However, societal gains from coordination will need to be reconciled with observations that it also leads to strategic simplification of the ecological food web, and generates both positive and negative impacts on individual sectors and non-target species.