Pathways towards a sustainable future envisioned by early-career conservation researchers

Scientists have warned decision-makers about the severe consequences of the global environmental crisis since the 1970s. Yet ecological degradation continues and little has been done to address climate change. We investigated early-career conservation researchers' (ECR) perspectives on, and prioritization of, actions furthering sustainability. We conducted a survey (n = 67) and an interactive workshop (n = 35) for ECR attendees of the 5th European Congress of Conservation Biology (2018). Building on these data and discussions, we identified ongoing and forthcoming advances in conservation science. These include increased transdisciplinarity, science communication, advocacy in conservation, and adoption of a transformation-oriented social–ecological systems approach to research. The respondents and participants had diverse perspectives on how to achieve sustainability. Reformist actions were emphasized as paving the way for more radical changes in the economic system and societal values linked to the environment and inequality. Our findings suggest that achieving sustainability requires a strategy that (1) incorporates the multiplicity of people's views, (2) places a greater value on nature, and (3) encourages systemic transformation across political, social, educational, and economic realms on multiple levels. We introduce a framework for ECRs to inspire their research and practice within conservation science to achieve real change in protecting biological diversity.</p

Implementation of the land-sharing and land-sparing framework in agro-ecological corridors

Maintaining adequate food supply while conserving biodiversity is one of the great challenges in conservation today. There is a fundamental controversy between land sparing and land sharing[1]: Land sparing favors intensive agriculture that allows maximal food production in a small area and spares land for conservation, while land sharing favors agro-environmental practices that create multifunctional agroecosystems. While land sparing has proven more advantageous in intact forests, evidence from long-history agricultural landscapes is mixed[2]. Using the sparing-sharing framework, we assessed costs and benefits of agriculture and conservation in planning an ecological corridor in the Jezreel Valley, Israel. We compared land sharing - using environmentally-friendly practices to create a corridor (100 km2) -- with land sparing of wide, intact natural patches (50-300m). To assess these two alternatives, we surveyed biodiversity of five taxonomic groups throughout the agricultural season in six common crops, across two land-sharing practices (uncultivated field-margins and reduced-tillage), and large, spared natural patches. Then we assessed the economic costs (profit and revenue) of these alternatives. Results indicate that uncultivated field-margins are highly biodiverse, despite suffering from a high level of disturbance. Surprisingly, arthropods (ground-dwelling arthropods, butterflies and parasitic wasps) show higher or similar diversity in field-margins as compared to natural patches. This pattern is not consistent with diversity of plants and birds, which is higher in natural patches. Composition analysis shows unique communities in field-margins and higher species turnover for arthropods, emphasizing field-margins contribution at large-scales. Unlike field-margins, reduced-tillage did not affect biodiversity. Economically, field-margins are correlated with higher revenue of some crops, which could be attributed to the pest-control services they provide. Our results indicate that in long-history agricultural landscapes, sparing is better than sharing in creating ecological corridors, but the optimal strategy is a combination of both. Thus, wide, natural patches should be the foundation of the agro-ecological corridor because they support the greatest biodiversity. In addition, field-margins make a better land-sharing strategy than reduced tillage; we found that reduced tillage did not affect biodiversity, regardless of its benefit in reducing soil erosion. The addition of field-margins further improves biodiversity, increasing habitat diversity in the landscape, and enhancing pest-control services that provide economic benefit to farmers. [1] Phalan et al. 2011. Reconciling food production and biodiversity conservation: land sharing and land sparing compared. Science. [2] von Wehrden et al. 2014. Realigning the land-sharing/land-sparing debate to match conservation needs: Considering diversity scales and land-use history. Landscape Ecol.peerReviewe

Quantifying Competitive Exclusion and Competitive Release in Ecological Communities: A Conceptual Framework and a Case Study

<div><p>A fundamental notion in community ecology is that local species diversity reflects some balance between the contrasting forces of competitive exclusion and competitive release. Quantifying this balance is not trivial, and requires data on the magnitude of both processes in the same system, as well as appropriate methodology to integrate and interpret such data. Here we present a novel framework for empirical studies of the balance between competitive exclusion and competitive release and demonstrate its applicability using data from a Mediterranean annual grassland where grazing is a major mechanism of competitive release. Empirical data on the balance between competitive exclusion and competitive release are crucial for understanding observed patterns of variation in local species diversity and the proposed approach provides a simple framework for the collection, interpretation, and synthesis of such data.</p></div

Results of ordination analysis (Nonmetric Multidimensional Scaling, NMDS) showing the effect of treatment (grass removal, grazing, and control) on forb species composition in the two habitats (valleys <i>vs</i>. slopes).

<p>Analyses were performed at the cluster scale (1m²) using the Jaccard index as a measure of dissimilarity.</p

The CR-CE space as a framework for analyzing the balance between competitive release and competitive exclusion.

<p>Systems in which the releasing factor fully compensates for competitive exclusions fall on the line y = x (the 'compensation line', points A and B in (a)). Systems characterized by partial compensation fall below the compensation line (C, D, E in (a)). Note that points C and D have the same effectiveness although they differ in the magnitude of competitive exclusion. Point E shows a lower effectiveness than points C and D although the magnitude of competitive release is similar to point D. If data on both forces are available for a set of sites within the same system, the effectiveness of the releasing factor can be expressed by the slope of a linear regression fitted to the data (b).</p

A map of the experimental system and the sampling design.

<p>Blocks located on the slopes are marked by yellow dashed lines; blocks located in the valleys are marked by white dashed lines. In each habitat there are three blocks with three treatments per block (grazing, grass removal, and control) and four blocks with two treatments (grazing and control). Each plot is 20x20m, but sampling was limited to the inner area of 10x10m. This area was sampled by 25 quadrates of 0.04m² organized in five clusters of 1m². Clipping experiments were conducted in the peripheral areas of control plots.</p

Results of a small-scale clipping experiment mimicking the effect of biomass removal by the cattle on the vegetation in the study area (removal of all shoots higher than 7 cm).

<p>The experiment was conducted within experimental units of 0.16m² protected from grazing (see Appendix B in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160798#pone.0160798.s005" target="_blank">S1 File</a> for details). (a, e) Clipped biomass of forbs and grasses in the two habitats. (b, f) Seedling mortality. (c, g) Extinction rates. (d, h) Species richness at the end of the growing season. Bars represent 95% confidence levels. Significant differences between clipped biomass of grasses and forbs (a, c) and between clipping treatments (b-d, f-h) are marked by asterisks.</p

Effects of grazing and grass removal on forb richness in the study system.

<p>(a) A summary of the experimental results using the CR-CE framework. The dashed line is the compensation line (y = x). Each point represents a certain combination of habitat, block, and scale. Each line is a regression line fitted to a different scale (0.04m²: <i>R</i>² = 0.63, <i>P</i> = 0.059; 1m²: <i>R</i>² = 0.82, <i>P</i> = 0.012; 100m²: <i>R</i>² = 0.54, <i>P</i> = 0.095, all slopes are significantly lower than 1 and all intercepts do not differ significantly from zero, significance levels based on standard errors of the regression coefficients). (b) Effect size (log response ratio) of the grass removal and grazing treatments under each combination of habitat (slopes <i>vs</i>. valleys) and scale (0.04, 1, and 100m²). Log response ratio is quantified as Log(<i>S</i>_TREATMENT/<i>S</i>_CONTROL), where <i>S</i> = mean number of forb species under the relevant combination of treatment, habitat and scale.</p

Butterflies are not a robust bioindicator for assessing pollinator communities, but floral resources offer a promising way forward

Monitoring pollinators is crucial for the evaluation of biodiversity and potential pollination services. Yet, efficiently monitoring multiple taxa over large areas can be costly. An alternative approach is using simple species bioindicators that represent the entire pollinator community. One of the requirements of a good bioindicator is that it can be easily identified to lower taxonomic levels and be sensitive to changes in habitat. This is the case for butterflies, a taxon for which many countries have a country-wide long-term monitoring scheme. We tested whether butterfly diversity can be used to predict diversity of bees and hoverflies both spatially and temporally. We surveyed 42 transects of the Dutch Butterfly Monitoring Scheme in 2020, to record species richness and abundance of butterflies, bees and hoverflies. We also recorded flower area and richness in the pollinator transects. To test whether pollinators with similar functional traits are more closely correlated than the entire pollinator community, we categorized bee and butterfly species according to their diet breadth (polyphagous vs. non-polyphagous), nitrogen-affinity (nitrophobous vs. nitrophilous larval resources) and body size. We used the same methods to test for temporal correlations over seven years for one site in Spain. Butterfly richness was not spatially correlated with bee richness (Pearson's r = 0.13), nor were the two taxa temporally correlated (Pearson's r = 0.02). Interestingly, hoverfly richness was spatially correlated with butterfly richness (Pearson's r = 0.43) and with bee richness (Pearson's r = 0.36) in the Netherlands and, hence, hoverflies might be slightly more suitable as a bioindicator of pollinator diversity in this area. Abundance of all three taxa showed no significant inter-correlation, except for correlations between diet specialist bees and butterflies (Pearson's r = 0.39). Importantly, all three taxa were strongly correlated with flower richness, but they varied in their preferences for host plant families. This is in line with 75% of the plant-pollinator studies finding significant positive relations. For monitoring schemes to be effective in informing better pollinator conservation, they should expand to include bees and hoverflies as well as simple indicators of habitat quality such as floral resources