The study was led by Jessica Forrest, full professor in the Department of Biology at uOttawa’s Faculty of Science, with lead author Gil Miranda, a former postdoctoral researcher in her laboratory who is now with Agriculture and Agri-Food Canada. Over two summers, the team surveyed rural roadsides in neighbouring jurisdictions around Ottawa, Ontario, where different levels of government maintain vegetation under visibly different regimes. The work was funded through an NSERC Alliance grant and carried out in partnership with Agriculture and Agri-Food Canada and the Canadian Wildlife Federation, whose staff helped conceive and fund the study as part of its Rights-of-Way as Habitat program.

The comparison hinged on a natural experiment created by administrative boundaries. Lanark County mows its roadsides twice a year and spot-treats only invasive plants such as wild parsnip. The City of Ottawa and the United Counties of Leeds and Grenville, by contrast, mow up to four times a year and apply herbicide more broadly across the right-of-way. Because these jurisdictions sit side by side and share similar soils, climate, and surrounding farmland, the researchers could compare otherwise similar roadside sites and isolate the effect of management alone. The Canadian Wildlife Federation helped pinpoint site pairs that shared comparable surrounding landscapes but fell under different mowing regimes, strengthening the design.

The fieldwork was exhaustive. Miranda netted and identified 3,773 pollinator specimens across 31 sites, a collection that ultimately totaled 153 species: 100 bee species and 53 flower fly species. Species identifications were confirmed through DNA barcoding led by Sophie Cardinal of Agriculture and Agri-Food Canada, a step that matters enormously in pollinator research, where many species are morphologically similar and easily confused in the field. The numbers told a consistent story. Low-intensity roadsides averaged 27 species per site across the study, while conventionally managed roadsides averaged 22. Abundance followed the same pattern, with far more bees and flower flies recorded along the less intensively maintained corridors.

For Forrest, the magnitude of the effect was the striking part. “Roadsides aren’t places most people think of as wildlife habitat, but they add up to a huge amount of land across the country,” she explained. “What surprised us wasn’t that management mattered; it was how much difference two modest changes made.” The finding reframes roadside vegetation from a liability to be kept tidy into an asset that can be managed cheaply for biodiversity. In agricultural regions, where natural habitat has been largely converted to cropland, these unmowed strips may represent some of the last reliable patches of nesting substrate and forage available to wild bees and hoverflies.

The mechanism behind the result is straightforward ecology. Frequent mowing removes flowering plants before they can bloom, eliminating the nectar and pollen resources that adult pollinators depend on throughout the growing season. It also destroys nest sites for ground-nesting bees and can kill larvae developing in stems. Broad herbicide spraying compounds the damage by suppressing the very flowering forbs, including many native species, that pollinators feed on. Reducing mowing to twice a year allows a community of flowering plants to establish and complete their life cycles, while targeted spot treatment of invasive species such as wild parsnip controls problem plants without stripping out the rest of the vegetation community.

Importantly, the researchers are not arguing that roadsides should be abandoned altogether. “Roads still need to be safe to drive, and invasive species still need to be managed,” Forrest noted. “But our results suggest land managers don’t have to choose between that and supporting pollinators. Mowing less often and spraying herbicide only where it’s actually needed rather than across a whole roadside, gets you most of the way there.” Safety sightlines, drainage, and invasive plant control can all be preserved under a low-intensity regime; the key insight is that blanket maintenance across an entire right-of-way delivers little extra benefit for road safety while imposing a substantial cost on insect communities.

The timing of the findings could hardly be more relevant. Bee and flower fly populations face mounting pressure across North America, squeezed by habitat loss, pesticide exposure, disease, and climate change. A recent continental assessment found that more than one-fifth of native pollinator species are now at elevated risk of extinction. Pollinators underpin the reproduction of a large share of flowering plants and contribute substantially to the yields of many fruit, vegetable, and seed crops, so their decline carries consequences well beyond entomology. Against that backdrop, the Ottawa-area results offer what Forrest describes as a rare bit of good news: a low-cost intervention within reach of virtually any municipality or county that maintains rights-of-way.

That accessibility is arguably the study’s most powerful message. “You don’t need to plant anything new or spend more money to see a benefit,” Forrest concluded. “You just need to let the roadside be a little less tidy.” Unlike pollinator initiatives that require seed mixes, planting programs, or expensive restoration, the changes tested here are essentially cost-saving: fewer mowing passes mean less fuel, labour, and equipment wear, and precision spraying means less herbicide purchased and applied. The study, titled “Roadside pollinator populations and the negative impact of intensive roadside vegetation maintenance,” was authored by Gil Miranda, Tracey Etwell, Vincent Fyson, Sophie Cardinal, Carolyn Callaghan, and Jessica Forrest, and was conducted with the support and cooperation of the City of Ottawa, Lanark County, and the United Counties of Leeds and Grenville.

For the thousands of kilometres of rural road crisscrossing farmland and forest across Canada and the United States, the implications are hard to ignore. A modest revision to maintenance schedules and spray protocols, decided at the level of a county public works department, could convert an entire network of roadside strips into connected habitat threads running through otherwise intensively used landscapes. As researchers and conservation groups continue to search for scalable responses to pollinator decline, the Ottawa study suggests that one of the most effective tools available may already be parked in the municipal maintenance shed, waiting to be deployed a little less often.

Subject of Research: Effects of roadside vegetation maintenance intensity on pollinator abundance and diversity

Article Title: Mowing less, spraying smarter gives pollinators a boost

Article References: Mowing less, spraying smarter gives pollinators a boost. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: pollinators, roadsides, bees, flower flies, mowing, herbicide, biodiversity, habitat management, Insect Conservation and Diversity, University of Ottawa, conservation, rights-of-way

Semi-natural grasslands are among the most endangered ecosystems on the continent. Unlike natural grasslands, they exist only because humans have mowed, grazed, and managed them for centuries, preventing forest from reclaiming the land. Across temperate Europe, these meadows shelter rare and endangered plant and animal species, which is why many have been placed under legal protection and long-term monitoring. Yet as intensive agriculture expands and traditional farming becomes economically unviable, these communities are vanishing at an alarming rate, making it urgent to understand exactly which factors sustain their diversity.

To address this question, Tomasz Wójcik of the University of Rzeszów and Alina Stachurska-Swakoń of Jagiellonian University selected the Wielopolka catchment as a model area because traditional low-intensity agriculture still survives there. Between 2012 and 2015, the team established 15 study sites arranged along the profiles of the main river valley and its tributaries, capturing the full range of grassland communities in the region. At each site, they recorded ten phytosociological relevés using the classical Braun-Blanquet method on 100-square-meter plots, yielding 150 vegetation plots in total. Alongside the botanical surveys, they dug 15 soil profiles to depths of 50 to 100 centimeters and collected 51 soil samples for laboratory analysis of texture, pH, organic matter, nitrogen, and the available forms of key nutrients including phosphorus, potassium, magnesium, and calcium.

The plant communities documented in the study spanned a remarkable edaphic range within a small area. Six associations and eight variants belonging to the Molinio-Arrhenatheretea class were distinguished, stretching from the wet rush community Scirpetum sylvatici in waterlogged valley bottoms to strikingly dry, thermophilous variants of the hay-meadow association Arrhenatheretum elatioris on valley tops. These thermophilous variants, hosting warm-loving species such as Gentiana cruciata, Melampyrum arvense, and Centaurea scabiosa, are rare in the northern part of the Western Carpathians and turned out to be the richest communities in the entire catchment, recording the highest values of all diversity indices measured.

Using discriminant analysis on Ellenberg ecological indicator values, the researchers identified the dominant environmental forces organizing this vegetation mosaic. Soil moisture, expressed as the moisture index, emerged as the single most powerful factor underlying community differentiation, followed by soil fertility. Crucially, these soil properties were themselves strongly correlated with position in the valley profile: moisture and fertility peaked in valley bottoms where humus-rich colluvial and alluvial soils accumulate, while the driest and most calcium-rich substrates occurred on upper slopes and hilltops. Altitude played only a secondary role at this relatively low elevation, and slope and exposure mattered even less, underscoring that at the landscape scale of a small catchment, the geometry of the valley itself dictates where water and nutrients collect.

The detailed soil chemistry added further nuance. Canonical Correspondence Analysis with forward selection and Monte Carlo permutation tests revealed that available phosphorus, measured as P2O5, was the most influential single soil parameter, explaining 8.4 percent of the variance in species composition with 23.8 percent of the contribution among soil variables. Alongside CaO, K2O, potassium, and the carbon-to-nitrogen ratio, phosphorus helped separate the thermophilous meadow variants from their neighbors. Intriguingly, while these nutrients governed which communities occurred where, only the C/N ratio showed a positive correlation with species richness itself, and no linear relationship was found between soil pH or total nitrogen and diversity measures. The concentration of calcium carbonate in the substrate, however, proved closely tied to the development of the xerothermic species that make the thermophilous meadows so exceptional.

The human dimension of the story proved just as decisive as the environmental one. The researchers identified six management types across the catchment, ranging from complete abandonment to regular mowing up to three times per year and occasional cattle grazing. Analysis of variance showed that unmanaged plots consistently recorded the lowest species richness, Shannon-Wiener diversity, and evenness, a result that was highly significant statistically. At the other end of the spectrum, patches of the wet meadow association Cirsietum rivularis that were mown three times per year achieved the highest Shannon-Wiener index in the entire study area, while the species-rich thermophilous meadows thrived under occasional mowing or sporadic grazing. Moderately frequent disturbance, it seems, keeps competitive grasses in check and opens space for the many light-demanding forbs that give these meadows their celebrated floristic wealth.

These findings align with a broader body of European research showing that low-intensity management creates the medium-level disturbances necessary to maintain high species richness, and that cessation of use triggers a predictable downhill slide: vegetation grows taller, mesophilic grasses expand, photophilous species retreat, and overall biodiversity declines as secondary succession advances toward woodland. The Wielopolka study also confirms patterns reported from other Carpathian regions, including the Sądecki Beskid Mountains and the White Carpathians, where dry grasslands on calcium-rich soils consistently harbor the greatest local species richness. When all environmental variables, soil traits, landscape indicators, and management types were combined in the ordination model, soil moisture, CaO content, and management type together explained the largest share of variation in species distribution, and the full model accounted for roughly half of the total variance in the data set.

The implications reach far beyond one Polish river basin. The authors argue that submontane landscapes, even within a relatively small area, can serve as crucial reservoirs of plant diversity and refuge for rare and protected species, provided the fine-grained mosaic of wet valley bottoms, dry slopes, and varied management is maintained. But there is a catch: the extensive grazing and varied mowing regimes that sustain this diversity are no longer profitable for landowners, and without systemic political and economic support, they are being abandoned. The study therefore delivers a clear message to policymakers across Central and Eastern Europe, where similar submontane grasslands persist: conserving these biodiversity hotspots requires not just designating protected areas, but actively subsidizing the traditional agricultural practices on which centuries of accumulated diversity ultimately depend. As climate change adds further pressure, with mountain plant communities responding unevenly to warming, the window for preserving these living archives of European cultural landscape is narrowing, and the Wielopolka catchment shows precisely what is at stake if that window closes.

Subject of Research: Factors determining plant diversity of semi-natural submontane grasslands in relation to soil properties and traditional management

Article Title: Grassland diversity of submontane valleys under influence of soil and management types

Article References: Wójcik, T., & Stachurska-Swakoń, A. (2026). Grassland diversity of submontane valleys under influence of soil and management types. Plant and Soil. https://doi.org/10.1007/s11104-026-09024-2

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09024-2

Keywords: grassland diversity, soil moisture, Western Carpathians, traditional management, semi-natural meadows, species richness, soil chemistry, calcium content, mowing, grazing, biodiversity conservation, Molinio-Arrhenatheretea