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The ecologist who wants to map everything
Abstract
Thomas Crowther wants to restore the planet, but first he needs to know how many trees, fungi, worms and microbes live on it. Thomas Crowther wants to restore the planet, but first he needs to know how many trees, fungi, worms and microbes live on it. Thomas Crowther at his lab at ETH Zurich
... Without them, the results of meta-analyses will be at best not reproducible, but at worst scientifically and empirically dubious. This situation may stem from informal observations being falsely conflated with natural history [6], when in reality natural history requires the meticulous curation of specimens. Without the sometimes maligned practice of natural history, the results of large-scale data analyses may be unrepeatable, unreliable or even invalid [7]. ...
The need for open, reproducible science is of growing concern in the twenty-first century, with multiple initiatives like the widely supported FAIR principles advocating for data to be Findable, Accessible, Interoperable and Reusable. Plant ecological and evolutionary studies are not exempt from the need to ensure that the data upon which their findings are based are accessible and allow for replication in accordance with the FAIR principles. However, it is common that the collection and curation of herbarium specimens, a foundational aspect of studies involving plants, is neglected by authors. Without publicly available specimens, huge numbers of studies that rely on the field identification of plants are fundamentally not reproducible. We argue that the collection and public availability of herbarium specimens is not only good botanical practice but is also fundamental in ensuring that plant ecological and evolutionary studies are replicable, and thus scientifically sound. Data repositories that adhere to the FAIR principles must make sure that the original data are traceable to and re-examinable at their empirical source. In order to secure replicability, and adherence to the FAIR principles, substantial changes need to be brought about to restore the practice of collecting and curating specimens, to educate students of their importance, and to properly fund the herbaria which house them.
Drones or unpersonned aerial vehicles are deployed towards the task of forestry, agriculture, and forest monitoring. Proponents claim that drone-assisted forest management increases forest yield. Detractors say that drone forestry is an instrument for biopolitical control and the transformation of mature forests into plantations. This article brings together the concept of the Plantationocene, an era marked by the iniquitous movement of people and seeds, with scholarship on the pharmakon, or the poisonous as well as therapeutic potentials of technologies, to interpret ethnographic field research with drone activists and drone engineers in Indonesia. The result is an argument for an ambivalent approach to emergent technologies–while drones are tools for control, they also enable operations for multispecies futures.
The Confederated Colville Tribes collaborated with DroneSeed, a forestry drone start-up, to use drones to replant their tribal forest after a devastating fire. Using concepts from Bernard Stiegler to interrogate ethnographic data, this article argues that forestry drones are pharmaka: their biopolitics can be therapeutic, that is, negentropic, capable of reversing ecological simplification. Drone forestry is a type of arborescent governmentality, a tree-based computer-coded attempt to control the growth of a forest. For the Colville, this negentropy is also an act of sovereignty that protects culture and honors multispecies relationships. For DroneSeed, it is an experiment in negentropic geoengineering, an attempt to profitably leverage technologies and biological regeneration to sequester carbon and reduce global existential risk. Ultimately the project was not the success desired; the failure of technoliberal projects that blend ecological and economic liberalism shows that a more radical approach might be necessary to root carbon and slow capitalism.
Mapping aboveground forest biomass is central for assessing the global carbon balance. However, current large-scale maps show strong disparities, despite good validation statistics of their underlying models. Here, we attribute this contradiction to a flaw in the validation methods, which ignore spatial autocorrelation (SAC) in data, leading to overoptimistic assessment of model predictive power. To illustrate this issue, we reproduce the approach of large-scale mapping studies using a massive forest inventory dataset of 11.8 million trees in central Africa to train and validate a random forest model based on multispectral and environmental variables. A standard nonspatial validation method suggests that the model predicts more than half of the forest biomass variation, while spatial validation methods accounting for SAC reveal quasi-null predictive power. This study underscores how a common practice in big data mapping studies shows an apparent high predictive power, even when predictors have poor relationships with the ecological variable of interest, thus possibly leading to erroneous maps and interpretations.
In a time of environmental crisis and ‘fake news’, there are calls for scientists to engage in public debate or advocacy. Some are wary, fearing that revealing subjective views poses a risk to scientific credibility or erodes trust in scholarly publishing. Others are less concerned, seeing it as their duty to society or an opportunity to boost their profile. Ideally, we need better checks and balances that allow scientists to contribute to public discourse without fear of compromising the credibility of their science, while avoiding subjective views influencing the outcomes of peer-reviewed research. For better or worse, scientists have personal views. The question is not whether they should be condoned or condemned, but how they should be managed in the context of scholarly publishing to maximise benefits and minimise negative outcomes. Using the recent contention around global tree ‘restoration’ potential as an example, I propose we score journals and articles based on the Transparency and Openness Promotion (TOP) guidelines and associated criteria. A high TOP score means readers have sufficient access to information to assess the objectivity and credibility of scientific publications and their authors. I show that current practice provides very little access to information, and readers are essentially being asked to have faith in the scholarly publication system. We must do better.
Significance:
• Science is predicated upon objectivity, yet readers are rarely given enough information to assess the objectivity, and thus integrity, of peer-reviewed research.
• To address this issue, a scoring system is proposed, which is based on the principles of transparency and openness.
• Improving transparency and openness in scholarly publishing is essential for allowing readers to assess the objectivity of published research and researchers, growing public trust, and allowing researchers to engage in public debates without fear of loss of scientific credibility.
Soil organisms are a crucial part of the terrestrial biosphere. Despite their importance for ecosystem functioning, few quantitative, spatially explicit models of the active belowground community currently exist. In particular, nematodes are the most abundant animals on Earth, filling all trophic levels in the soil food web. Here we use 6,759 georeferenced samples to generate a mechanistic understanding of the patterns of the global abundance of nematodes in the soil and the composition of their functional groups. The resulting maps show that 4.4 ± 0.64 × 10²⁰ nematodes (with a total biomass of approximately 0.3 gigatonnes) inhabit surface soils across the world, with higher abundances in sub-Arctic regions (38% of total) than in temperate (24%) or tropical (21%) regions. Regional variations in these global trends also provide insights into local patterns of soil fertility and functioning. These high-resolution models provide the first steps towards representing soil ecological processes in global biogeochemical models and will enable the prediction of elemental cycling under current and future climate scenarios.
The potential for global forest cover
The restoration of forested land at a global scale could help capture atmospheric carbon and mitigate climate change. Bastin et al. used direct measurements of forest cover to generate a model of forest restoration potential across the globe (see the Perspective by Chazdon and Brancalion). Their spatially explicit maps show how much additional tree cover could exist outside of existing forests and agricultural and urban land. Ecosystems could support an additional 0.9 billion hectares of continuous forest. This would represent a greater than 25% increase in forested area, including more than 200 gigatonnes of additional carbon at maturity.Such a change has the potential to store an equivalent of 25% of the current atmospheric carbon pool.
Science , this issue p. 76 ; see also p. 24
A spatially explicit global map of tree symbioses with nitrogen-fixing bacteria and mycorrhizal fungi reveals that climate variables are the primary drivers of the distribution of different types of symbiosis.
The majority of the Earth’s terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming1, 2, 3, 4. Despite evidence that warming enhances carbon fluxes to and from the soil5, 6, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30 ± 30 petagrams of carbon to 203 ± 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12–17 per cent of the expected anthropogenic emissions over this period7, 8. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon–climate feedback that could accelerate climate change.
The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuous map of forest tree density at a global scale. This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.