Biology subjects

Nicholson, C. C.

Publications and source records attributed to Nicholson, C. C..

3 recordsLinked to original sources

bioRxiv2022

Mapping connectivity and conservation opportunity on agricultural lands across the conterminous United States

O_LIDepending on management practices, agricultural lands can either pose substantial barriers to the movement of native species or can support landscape connectivity by linking areas of high-quality habitat. Balancing connectivity and sustainable food production on agricultural lands is critical to conservation in the conterminous United States (CONUS) where agriculture makes up close to half of total land area. However, limited guidance exists on where to target conservation resources to maximize benefits for native species and food security. C_LIO_LITo quantify the potential contribution of agricultural lands to the movement of organisms, we developed a novel method for estimating agricultural management intensity (based on remotely sensed temporal variation in vegetation cover on croplands and pastures) and incorporated these estimates into a CONUS-wide, circuit-theory based model of ecological flow connectivity. We then combined our connectivity results with data on the productivity, versatility, and resilience of agricultural lands (PVR) to identify conservation opportunities that support both biodiversity and food production. C_LIO_LIThe highest levels of connectivity on agricultural lands occurred on relatively unmodified rangelands and on cropland and pasture in close proximity to large amounts of natural land cover. C_LIO_LIMapping connectivity and PVR across CONUS revealed 10.2 Mha of agricultural lands (2.7%) with high value for both connectivity and food production, as well as large amounts of agricultural land (>140 Mha in total) with high value for either cultivation or supporting biodiversity (e.g., through ecological restoration). C_LIO_LIDrawing on these findings, we provide recommendations on the types of conservation approaches most suitable for a given agricultural system and link these recommendations to specific government incentive programs. To help facilitate conservation planning based on our results, we have developed an interactive web application, allowing users to visualize the spatial data developed here within their regions of interest. C_LI

ecology↗

bioRxiv2021

A meta-analysis of single visit pollination effectiveness

Many animals provide essential ecosystem services in the form of plant pollination. A rich literature documents considerable variation in the single visit pollination effectiveness of different plant visitors, but this literature has yet to be comprehensively synthesized. We conducted a hierarchical meta-analysis of 193 studies and extracted 1716 single visit effectiveness (SVE) comparisons for 252 plant species. We paired SVE data with visitation frequency data for 75 of these studies. Given the global dominance of honeybees in pollinator communities, we used these data to ask: 1) Do honeybees (Apis mellifera) and other floral visitors vary in their SVE?; 2) To what extent do plant and pollinator attributes predict the difference in SVE between honeybees and other visitors?; and 3) Is there a correlation between floral visitation frequency and SVE? We found that honeybees were significantly less effective than the most effective non-honeybee pollinator. Although not significantly different, honeybees also tended to be less effective than the mean community effectiveness. Honeybees were less effective as pollinators of crop plants and when compared to birds and other bees. Visitation frequency and pollination effectiveness were positively correlated, but this trend was largely driven by data from communities where honeybees were absent, suggesting that honeybees generally combine high visitation frequency and lower SVE. Our study demonstrates that non-honeybee floral visitors are highly effective pollinators of many crop and non-crop plants. While the high visitation frequency typically displayed by honeybees undoubtably makes them important pollinators, we show that honeybees are slightly less effective than the average pollinator and rarely the most effective pollinator of the plants they visit. As such, honeybees may be imperfect substitutes for the loss of wild pollinators and safeguarding global crop production will benefit from conservation of non-honeybee taxa. Open Research StatementAlthough we are fully committed to data transparency, we are also aware of different research teams working on related meta-analyses. As such, we prefer to wait until our paper is accepted to make data publicly available but are happy to share data upon request. Data will be permanently archived on Figshare following acceptance.

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bioRxiv2020

Global relationships between crop diversity and nutritional stability

Nutritional stability - a food systems capacity to provide sufficient nutrients despite disturbance - is a critical feature of sustainable agriculture, especially in light of ongoing climate change. Yet, measuring nutritional stability has proven challenging. Addressing this challenge will help identify resilient food systems, detect shortcomings in nutrient availability, and evaluate if stability-focused interventions actually work. We develop a novel approach that uses 55 years of crop data across 184 countries to assemble over 22,000 bipartite crop-nutrient networks. We then quantify the tolerance of these networks to disturbance simulated via sequential crop loss (Fig. 1) and evaluate patterns of crop diversity and nutritional stability across countries, over time and between crop supply scenarios (imports versus in country production). We observe a positive, saturating relationship between crop diversity and nutritional stability across countries; however there is substantial variability between countries over time. Next, despite crop diversity gains since 1961, nutritional stability has remained stagnant or decreased in all regions except Asia. A decline in the average number of nutritional links per network (range: -3 to -18% across regions) and the aforementioned saturating relationship explain this counter-intuitive finding. Finally, we find that imports increase crop diversity and improve or sustain stability, indicating that nutrient availability is market exposed in many countries, particularly developing states. Although applied globally, our approach is applicable across levels of organization, from household intake to sub-national production, and provides a way forward for understanding the contributions of crop diversity to the stability of nutrients available for human consumption. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/227520v1_fig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@d6712forg.highwire.dtl.DTLVardef@a0cc45org.highwire.dtl.DTLVardef@c2d6bforg.highwire.dtl.DTLVardef@1a0a459_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1C_FLOATNO A new approach for understanding nutritional stability. The robustness of networks, such as a crop-nutrient network (a), can be gauged through assembling attack tolerance curves (b & c), whereby as nodes (i.e. crops) are eliminated constituent nutrients are lost. Of course, removal order matters (b vs c), therefore permuted combinations of crop loss generate average loss curves (see Methods). We use the area under this curve as our measure of nutritional stability (RN). Crop-nutrient networks with few redundant connections are susceptible to crop removal and can experience rapid nutrient loss (e.g. Maldives; d), whereas countries with a diverse food supply are more robust (e.g. China; e). This unitless metric is generalizable across different levels of aggregation (e.g. individual, household, community, national food system). C_FIG

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