• Energy Research

Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.

AbstractGrassland managers and scientists are increasingly interested in cost-effective alternative ways of grassland biodiversity conservation. Prescribed burning is a promising management tool which should be integrated in the planning of management efforts. In addition, small-scale prescribed burning is an effective fire suppression strategy to decrease the serious negative impacts of uncontrolled burnings on ecosystems and human life. Prescribed burning forms an integral part of the North-American grassland management practice, while in Europe it is rarely applied, despite the fact that uncontrolled burning occurs frequently in some regions. Our goal was to evaluate the use of prescribed burning as a promising but neglected management tool in European grasslands. We found that European studies on prescribed burning of grasslands are scarce and we conclude that annual burning is usually not an appropriate option for the conservation of species-rich grasslands. We reviewed burning studies from North-America to identify findings which might be adapted to the European grassland conservation strategy. In North-America, contrary to Europe, the application of burning is fine tuned in terms of frequency and timing, and usually combined with other restoration measures (grazing or seed sowing). Thus, we conclude that with the application of carefully designed prescribed burning, multiple conservation goals, e.g. invasion control and enhancing landscape-level heterogeneity, can be linked with an effective fire suppression strategy. We emphasize that for the application of prescribed burning in Europe, the general findings of carefully designed case studies should be combined with the practical knowledge of conservation managers concerning the local application circumstances to reach specific management objectives.

Restoration of degraded drylands is urgently needed to mitigate climate change, reverse desertification and secure livelihoods for the two billion people who live in these areas. Bold global targets have been set for dryland restoration to restore millions of hectares of degraded land. These targets have been questioned as overly ambitious, but without a global evaluation of successes and failures it is impossible to gauge feasibility. Here we examine restoration seeding outcomes across 174 sites on six continents, encompassing 594,065 observations of 671 plant species. Our findings suggest reasons for optimism. Seeding had a positive impact on species presence: in almost a third of all treatments, 100% of species seeded were growing at first monitoring. However, dryland restoration is risky: 17% of projects failed, with no establishment of any seeded species, and consistent declines were found in seeded species as projects matured. Across projects, higher seeding rates and larger seed sizes resulted in a greater probability of recruitment, with further influences on species success including site aridity, taxonomic identity and species life form. Our findings suggest that investigations examining these predictive factors will yield more effective and informed restoration decision-making.

Le pâturage représente l'utilisation la plus étendue des terres dans le monde. Pourtant, ses impacts sur les services écosystémiques restent incertains car des interactions omniprésentes entre la pression de pâturage, le climat, les propriétés des sols et la biodiversité peuvent se produire mais n'ont jamais été traitées simultanément. En utilisant une enquête standardisée sur 98 sites sur six continents, nous montrons que les interactions entre la pression du pâturage, le climat, le sol et la biodiversité sont essentielles pour expliquer la fourniture de services écosystémiques fondamentaux dans les zones arides du monde entier. L'augmentation de la pression de pâturage a réduit la prestation de services écosystémiques dans les zones arides plus chaudes et pauvres en espèces, tandis que les effets positifs du pâturage ont été observés dans les zones plus froides et riches en espèces. La prise en compte des interactions entre le pâturage et les facteurs abiotiques et biotiques locaux est essentielle pour comprendre le sort des écosystèmes des terres arides sous le changement climatique et l'augmentation de la pression humaine. El pastoreo representa el uso más extenso de la tierra en todo el mundo. Sin embargo, sus impactos en los servicios ecosistémicos siguen siendo inciertos porque las interacciones generalizadas entre la presión del pastoreo, el clima, las propiedades del suelo y la biodiversidad pueden ocurrir, pero nunca se han abordado simultáneamente. Utilizando una encuesta estandarizada en 98 sitios en seis continentes, mostramos que las interacciones entre la presión del pastoreo, el clima, el suelo y la biodiversidad son fundamentales para explicar la prestación de servicios ecosistémicos fundamentales en las tierras secas de todo el mundo. El aumento de la presión del pastoreo redujo la prestación de servicios ecosistémicos en las tierras secas más cálidas y pobres en especies, mientras que los efectos positivos del pastoreo se observaron en las zonas más frías y ricas en especies. Considerar las interacciones entre el pastoreo y los factores abióticos y bióticos locales es clave para comprender el destino de los ecosistemas de tierras secas bajo el cambio climático y el aumento de la presión humana. Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure. يمثل الرعي الاستخدام الأوسع للأراضي في جميع أنحاء العالم. ومع ذلك، لا تزال آثاره على خدمات النظام الإيكولوجي غير مؤكدة لأن التفاعلات المنتشرة بين ضغط الرعي والمناخ وخصائص التربة والتنوع البيولوجي قد تحدث ولكن لم تتم معالجتها أبدًا في وقت واحد. باستخدام مسح موحد في 98 موقعًا في ست قارات، نوضح أن التفاعلات بين ضغط الرعي والمناخ والتربة والتنوع البيولوجي ضرورية لشرح تقديم خدمات النظام الإيكولوجي الأساسية عبر الأراضي الجافة في جميع أنحاء العالم. أدى الضغط المتزايد للرعي إلى تقليل تقديم خدمات النظام الإيكولوجي في الأراضي الجافة الأكثر دفئًا والفقيرة بالأنواع، في حين لوحظت آثار إيجابية للرعي في المناطق الأكثر برودة والغنية بالأنواع. يعتبر النظر في التفاعلات بين الرعي والعوامل المحلية اللاأحيائية والأحيائية أمرًا أساسيًا لفهم مصير النظم الإيكولوجية للأراضي الجافة في ظل تغير المناخ وزيادة الضغط البشري.

Abstract Context Predicting how changes in weather patterns and land use jointly impact populations is a pressing task in ecology. Microclimate may play a key role in species’ local persistence by modulating regional weather effects. We lack sufficient empirical evidence to understand the relative effects of landscape structure and habitat conditions on intraspecific trait variation. Objectives Using a spatially and temporally replicated demographic dataset, we tested the relative effect of landscape structure (area and connectivity of remnant habitat fragments), microclimate (heat load), and fluctuation in weather conditions (study year) on intraspecific plant trait variation, and we investigated whether the local heat load modulated the weather effects on the studied traits. Methods We performed repeated measurements of stem height, leaf area, number of stems, main inflorescence length and number of primary side inflorescences of 569 permanently marked individuals of the grassland specialist Salvia nemorosa L. We sampled 13 populations encompassing microhabitats exposed to different heat load levels, over three consecutive years. Results Mature individuals had fewer stems in isolated, and taller stems in small habitat fragments. High levels of heat load and dry years affected negatively all measured traits, and the negative effects of exposure to high heat load were generally exacerbated in dry years. Conclusions Exposure to strong environmental stressors could ultimately obscure the real effect of human impact on plant populations. Landscape planning for conservation of dry grassland species should ensure not only improved habitat connectivity but also high-quality habitats with heterogeneous microclimates able to buffer weather extremes.

Earth harbours an extraordinary plant phenotypic diversity1 that is at risk from ongoing global changes2,3. However, it remains unknown how increasing aridity and livestock grazing pressure-two major drivers of global change4-6-shape the trait covariation that underlies plant phenotypic diversity1,7. Here we assessed how covariation among 20 chemical and morphological traits responds to aridity and grazing pressure within global drylands. Our analysis involved 133,769 trait measurements spanning 1,347 observations of 301 perennial plant species surveyed across 326 plots from 6 continents. Crossing an aridity threshold of approximately 0.7 (close to the transition between semi-arid and arid zones) led to an unexpected 88% increase in trait diversity. This threshold appeared in the presence of grazers, and moved toward lower aridity levels with increasing grazing pressure. Moreover, 57% of observed trait diversity occurred only in the most arid and grazed drylands, highlighting the phenotypic uniqueness of these extreme environments. Our work indicates that drylands act as a global reservoir of plant phenotypic diversity and challenge the pervasive view that harsh environmental conditions reduce plant trait diversity8-10. They also highlight that many alternative strategies may enable plants to cope with increases in environmental stress induced by climate change and land-use intensification.