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Reconciling crop production, climate action and nature conservation in Europe by agricultural intensification and extensification
Agricultural production in areas characterized by low productivity, steep slopes, and high fragmentation is usually associated with higher-than-average management costs and environmental impacts. Abandoning this suboptimal cropland to vegetation regrowth, while optimizing crop production in other locations, is an attractive strategy for supporting climate and biodiversity targets without compromising food security. However, it has not yet been explored within the specific context of European agriculture. Here, we identify the area extent of suboptimal cropland in Europe and assess if crop production losses from its revegetation can be compensated by implementing scenarios of cropland intensification or extensification elsewhere. We found 24.2 million hectares of suboptimal cropland, of which 66% is at degradation risk and about 50% is within biodiversity priority areas. Reducing agricultural intensity in 16.4–30.9 million hectares of the remaining cropland by introducing parcels of trees into the agricultural landscape (extensification), together with strategic crop-switching optimization, can entirely offset crop production losses from revegetation of suboptimal cropland. This scenario has the potential to mitigate up to 40% of European agricultural emissions of greenhouse gases and reduce cropland pressure on biodiversity by 20%. In contrast, cropland intensification achieves lower carbon-biodiversity benefits, with risks that crop losses are not fully compensated.
This paper analyzes the role of suboptimal cropland restoration, crop switching and extensification in reconciling production with climate and conservation goals in Europe, finding it could cut agricultural GHGs by ~40% and biodiversity loss by ~20%.
Journal Article
Long-term changes in northern large-herbivore communities reveal differential rewilding rates in space and time
Herbivores have important impacts on ecological and ecosystem dynamics. Population density and species composition are both important determinants of these impacts. Large herbivore communities are shifting in many parts of the world driven by changes in livestock management and exploitation of wild populations. In this study, we analyse changes in large herbivore community structure over 66 years in Norway, with a focus on the contribution of wildlife and livestock. We calculate metabolic biomass of all large-herbivore species across the whole region between 1949 and 2015. Temporal and spatial patterns in herbivore community change are investigated and we test hypotheses that changes in wildlife biomass are driven by competition with livestock. We find that total herbivore biomass decreased from 1949 to a minimum in 1969 due to decreases in livestock biomass. Increasing wild herbivore populations lead to an increase in total herbivore biomass by 2009. Herbivore communities have thus reverted from a livestock dominated state in 1949 (2% of large herbivore metabolic biomass comprised of wildlife species) to a state with roughly equal wildlife and livestock (48% of metabolic biomass comprised of wildlife species). Declines in livestock biomass were a modest predictor of wildlife increases, suggesting that competition with livestock has not been a major limiting factor of wild herbivore populations over the past decades. Instead there was strong geographic variation in herbivore community change, with milder lowland regions becoming more dominated by wild species, but colder mountain and northern regions remaining dominated by livestock. Our findings indicate that there has been notable rewilding of herbivore communities and herbivore-ecosystem interactions in Norway, particularly in milder lowland regions. However, Norwegian herbivores remain mostly regulated by management, and our findings call for integrated management of wild and domestic herbivores.
Journal Article
Predicted expansion of beaver pond distribution in Arctic Alaska, 1910–2090
Ecosystem engineering by beavers is a nascent disturbance in the Arctic tundra, appearing in the 1970s in western Alaska and since expanding deeper into tundra regions. Evidence from modeling and observations indicates that beaver ponds act as biophysical oases, and we anticipate myriad changes as these disturbances are constructed along tundra streams, sloughs, and lake outlets. We used over 11 000 mapped beaver pond locations in Arctic Alaska and their climatic, geographic, and environmental attributes to understand (1) which of those attributes control the distribution of beaver ponds, and, if temperature is a factor, (2) how beaver pond distribution will change under future climate scenarios. Of the variables used in the ensemble modeling approach, mean annual temperature was the most important variable in determining beaver pond locations, with pond occurrences more likely in warmer locales (>−2 °C). The distance to water was also important in determining beaver pond locations, as expected, with higher likelihood of ponds closer to water features. Lowland topographic variables were also relevant in determining the distribution of beaver ponds. Under the current climate, beaver ponds are widespread in most of western Alaska, matching the predicted extent of potential occupancy, with the exception of areas furthest from treeline, implying possible dispersal lags or other factors. By 2050, under future climate scenarios (RCP8.5; 2090 for RCP6.0), the entire North Slope of Alaska, which currently has no beaver ponds, is predicted to be suitable for beaver ponds, comparable to western Alaska in 2016. The vast extent of future beaver engineering in tundra regions will require reenvisioning the typical tundra stream ecosystems of northern Alaska, northern Canada, northern Europe, and northern Asia to include more extensive wetlands, routine disturbances, permafrost thaw, and other features of these nascent oases that are not fully understood.
Journal Article
Contrasting spatial, temporal and environmental patterns in observation and specimen based species occurrence data
Species occurrence data records the location and time of an encounter with a species, and is valuable for many aspects of ecological and evolutionary analyses. A key distinction within species occurrence data is between (1) collected and preserved specimens that can be taxonomically validated (i.e., natural history collections), and (2) observations, which are more error prone but richer in terms of number and spread of observations. In this study we analyse the distribution in temporal, spatial, taxonomic and environmental coverage of specimen- and observation based species occurrence data for land plants in Norway, a region with strong climatic and human population density gradients. Of 4.8 million species occurrence records, the majority (78%) were observations. However, there was a greater species richness in the specimen record (N = 4691) than in the observation record (N = 3193) and most species were recorded more as specimens than observations. Specimen data was on average older, and collected later during the year. Both record types were highly influenced by a small number of prolific contributors. The species most highly represented in the observation data set were widespread or invasive, while in the specimen records, taxonomically challenging species were overrepresented. Species occurrence records were unevenly spatially distributed. Both specimen and observation records were concentrated in regions of Norway with high human population density and with high temperatures and precipitation, but in different regions within Norway. Observation and specimen records thus differ in taxonomic, temporal, spatial and environmental coverage for a well-sampled group and study region, potentially influencing the ecological inferences made from studies utilizing species occurrence data. The distribution of observation data dominates the dataset, so inferences of species diversity and distributions do not correspond to the evolutionary or physiological knowledge of species, which is based on specimen data. We make recommendations for users of biodiversity data, and collectors to better exploit the complementary strengths of these distinct biodiversity data types.
Journal Article
Legacy effects of herbivory on treeline dynamics along an elevational gradient
Treelines are expected to expand into alpine ecosystems with global warming, but herbivory may delay this expansion. This study quantifies long-term effects of temporally varying sheep densities on birch recruitment and growth in the treeline ecotone. We examined treeline ecotone successional trajectories and legacy effects in a replicated experimental setup, where enclosures were present for 14 years with three different sheep densities (0, 25, 80 sheep km⁻²). Before and after the enclosures were present, the site had an ambient sheep density of 20–25 km⁻². We sampled field data 4 years after enclosure removal and compared these to data sampled 8 and 9 years after enclosure erection. We sampled data on birch browsing pressure, birch distribution across life-stages (recruits, saplings, and mature trees), and birch annual radial growth. Fourteen years of increased or decreased sheep density had observable legacy effects depending on birch life-stage. Birch recruit prevalence decreased in areas, where sheep were reintroduced after being absent for 14 years. For the same areas, sapling and mature tree prevalence increased, indicating that these areas have entered alternative successional trajectories compared to areas, where sheep were present the whole time. Birch annual radial growth showed a lag effect of 2 years after enclosure removal, with growth decreasing in areas where sheep had been absent for 14 years and increasing where sheep densities were high. Thus, decadal-scale absences of herbivores can leave legacy effects due to increased numbers of trees that have high resistance to later-introduced herbivore browsing.
Journal Article
Herbivory and climate as drivers of woody plant growth
Vegetation at ecotone transitions between open and forested areas is often heavily affected by two key processes: climate change and management of large herbivore densities. These both drive woody plant state shifts, determining the location and the nature of the limit between open and tree or shrub-dominated landscapes. In order to adapt management to prevailing and future climate, we need to understand how browsing and climatic factors together affect the growth of plants at biome borders. To disentangle herbivory and climate effects, we combined long-term tree growth monitoring and dendroecology to investigate woody plant growth under different temperatures and red deer (Cervus elaphus) herbivory pressures at forest–moorland ecotones in the Scottish highlands. Reforestation and deer densities are core and conflicting management concerns in the area, and there is an urgent need for additional knowledge. We found that deer herbivory and climate had significant and interactive effects on tree growth: in the presence of red deer, pine (Pinus sylvestris) growth responded more strongly to annual temperature than in the absence of deer, possibly reflecting differing plant–plant competition and facilitation conditions. As expected, pine growth was negatively related to deer density and positively to temperature. However, at the tree population level, warming decreased growth when more than 60% of shoots were browsed. Heather (Calluna vulgaris) growth was negatively related to temperature and the direction of the response to deer switched from negative to positive when mean annual temperatures fell below 6.0°C. In addition, our models allow estimates to be made of how woody plant growth responds under specific combinations of temperature and herbivory, and show how deer management can be adapted to predicted climatic changes in order to more effectively achieve reforestation goals. Our results support the hypothesis that temperature and herbivory have interactive effects on woody plant growth, and thus accounting for just one of these two factors is insufficient for understanding plant growth mechanics at biome transitions. Furthermore, we show that climate-driven woody plant growth increases can be negated by herbivory.
Journal Article
Long-term changes in herbivore community and vegetation impact of wild and domestic herbivores across Iceland
Changes in wild and domestic herbivore populations significantly impact extensive grazing systems, particularly in low productive environments, where increasing wild herbivore populations are perceived as a threat to farming. To assess the magnitude of these changes in Iceland, we compiled time series on herbivore populations from 1986 to 2020 and estimated changes in species densities, metabolic biomass, and consumption of plant biomass in improved lands and unimproved rangelands. We compared estimates of consumption rates to past and present net primary production. Overall, the herbivore community composition shifted from livestock to wildlife dominated. However, wild herbivores only contributed a small fraction (14%) of the total herbivore metabolic biomass and consumption (4–7%), and livestock dominated the overall herbivore biomass. These insights highlight the necessity of developing improved local integrated management for both wild and domestic herbivores where they coexist.
Journal Article
Species data for understanding biodiversity dynamics: The what, where and when of species occurrence data collection
1. The availability and quantity of observational species occurrence records have greatly increased due to technological advancements and the rise of online portals, such as the Global Biodiversity Information Facility (GBIF), coalescing occurrence records from multiple datasets. It is well‐established that such records are biased in time, space and taxonomy, but whether these datasets differ in relation to origin have not been assessed. If biases are specific to different types of datasets, and the relative contribution from these datasets have changed over time, these shifting biases will have implications for interpretations of results and, consequentially, for management and conservation measures. 2. We examined observational GBIF records from Norway to test potential differences in taxonomic, time and land‐cover biases between 10 different datasets, with a focus on red‐listed and non‐native species. 3. The datasets differ in their taxonomic coverage, with datasets dominated by citizen scientist recorders focusing greatly on birds. The number of records has increased over time; in particular, citizen science datasets have had a sharp increase in recent years. 4. The different datasets (including division of the datasets by conservation status) showed differences in geographical coverage. Anthropogenic land covers have more records than would be expected by chance in the majority of cases. Remote areas have fewer records than would be expected, underlining the prevalence of a roadside bias. 5. Accounting for biases in opportunistic species occurrence records need to be a dynamic rather than static process, as the taxonomic and geographical biases have changed over time and differ between datasets, depending on origin and inherent characteristics. Data‐collection programmes should be designed to counteract the biases of the specific datasets, and methods to account for the biases in existing data should be developed. When utilizing compiled, open‐source data, care must be taken to ensure complementarity between the datasets, both regarding time and space. Incorporating strengths and accounting for biases between datasets can strengthen the integration between species occurrence records with different origins for science‐policy impact and management. Datasets stored in GBIF differ in their taxonomic‐, temporal‐ and geographic biases, depending on origin of the dataset. Anthropogenic land‐covers have more records than would be expected by chance and, remote areas have fewer records than would be expected, underlining the prevalence of a roadside bias.
Journal Article
The trophic distribution of biomass in ecosystems with co-occurring wildlife and livestock
Trophic interactions regulate populations, but anthropogenic processes influence primary productivity and consumption by both herbivore and carnivore species. Trophic ecology studies often focus on natural systems such as protected areas, even though livestock globally comprise the majority of terrestrial vertebrate biomass. Here we explore spatial and temporal patterns in the distribution of biomass between plants, and large herbivores and carnivores (> 10 kg) in Norwegian rangelands, including both wildlife and livestock. We find high spatial variation in the relationship between plant and herbivore biomass, with both positive and negative divergence in observed biomass from expectations based on primary productivity. Meanwhile, despite recent partial recoveries in carnivore densities across Norway, carnivore biomass is still lower than expected based on herbivore biomass, even if livestock are excluded from the estimation. Our study highlights how temporal trends in both herbivores and carnivores reflect policy development. The role of livestock husbandry and wildlife management is thus key in determining realised biomass distributions in anthropogenically influenced ecosystems.
Journal Article