Kathryn E. Freemark

Aquatic phyto-toxicity of 23 pesticides applied at expected environmental concentrations

Abstract Environment Canada uses an Expected Environmental Concentration (EEC) in evaluating the hazard of pesticides to nontarget aquatic organisms. This concentration is calculated by assuming an overspray of a 15 cm deep waterbody at the label application rate. The EEC of pesticides is then related to the EC50 (concentration causing a 50% reduction in a chosen toxicity endpoint) for a given aquatic test organism. At present, the use of an uncertainty factor is suggested in the literature if only a few species are tested because of important interspecific differences in pesticide sensitivity. The phytotoxicity of the EEC of 23 different pesticides to ten algae (24 h inhibition of 14C uptake) and one vascular plant (7-day growth inhibition) was determined in an effort to examine the question of interspecific sensitivity and its relation to the development of pesticide registration guidelines. Chemicals included five triazine herbicides (atrazine, cyanazine, hexazinone, metribuzin, and simazine), four sulfonylurea herbicides (chlorsulfuron, metsulfuron-methyl, ethametsulfuron-methyl, triasulfuron), two phenoxyalkane herbicides (2,4-D and MCPA), two pyridine herbicides (picloram and triclopyr), a substituted urea, an amine derivative, and an imidazolinone herbicide (tebuthiuron, glyphosate and imazethapyr, respectively), a bipyridylium (diquat), a hydroxybenxonitrile (bromoxynil), an aldehyde (acrolein) and an acetanilide (metolachlor) herbicide, as well as two carbamate insecticides (carbofuran and carbaryl) and a triazole derivative fungicide (propiconazole). Test organisms were selected based on ecological relevance and present use in test protocols. Organisms included green algae (Scenedesmus quadricauda and Selenastrum capricornutum), diatoms (Nitzschia sp. and Cyclotella meneghiana), cyanobacteria (Microcystis aeruginosa, Oscillatoria sp., Pseudoanabaena sp., Anabaena inaequalis and Aphanizomenon flos-aquae) and a floating vascular plant, duckweed (Lemna minor). The five triazine herbicides, acrolein and diquat inhibited the carbon uptake of all algae, diatoms and cyanobacteria by more than 50%. Two other pesticides, carbaryl and tebuthiuron, caused more than 50% inhibition in 90% of the algae tested. Nine of the 23 pesticides, five of which were triazine herbicides, were therefore highly phytotoxic to algae. Twelve pesticides inhibited growth of duckweed by more than 50%. Once again, all five of the triazine herbicides were among this group, as well as three sulfonylurea herbicides and acrolein, diquat, metolachlor and tebuthiuron. Duckweed was the most sensitive organism tested, being equally affected by all pesticides causing algal phytotoxicity (with the exception of carbaryl), as well as being acutely affected by sulfonylurea herbicides. Green algae were least sensitive to diquat; diatoms and one cyanobacterium were the only organisms that showed sensitivity to glyphosate. Through testing the phytotoxicity of a variety of agricultural pesticides to a wide range of algal taxa, it is evident that there are considerable differences in sensitivity among species and that the use of an uncertainty factor is necessary to provide an acceptable margin of safety in evaluating the hazard presented by these chemicals to the aquatic environment.

Impacts of agricultural herbicide use on terrestrial wildlife in temperate landscapes: A review with special reference to North America

Abstract The existing literature was examined to assess the extent to which wildlife (plants, soil organisms, above-ground insects/arthropods, mammals, birds) living in terrestrial habitats has been affected by use of agricultural herbicides in temperate landscapes. Although North America was of special interest for regulatory reasons, the review was extended to western Europe because the most extensive and intensive work has been done there. The half-life of herbicides in the environment ranges from less than 1 month to more than 1 year. Wildlife within fields is most likely to be exposed to herbicides, particularly when fields are planted with crops (e.g. corn, soybean, wheat, cotton) which are routinely sprayed. Wildlife is also likely to be exposed in non-crop habitats adjoining croplands, primarily from direct overspray (especially during aerial application), and drift during and/or volatilisation after application. The most conclusive scientific evidence for direct effects of herbicides on arable weeds, and associated indirect effects on insects and birds exists in the United Kingdom. Evidence for similar effects in North America is primarily circumstantial at present. Little work has been done anywhere on impacts of herbicides on plants and their associated fauna in non-crop habitats adjoining treated fields. Chemical farming (in particular, the use of herbicides) has dramatically altered the habitat pattern of temperate landscapes in North America and western Europe. Strong evidence exists for adverse effects of changes in habitat pattern on beneficial insects and arthropods in the United Kingdom, and on birds in North America and western Europe. Toxicity testing guidelines for non-target plant protection need to be developed and enforced to support pesticide registration. In addition, research is needed to include more ecologically relevant plant species in laboratory tests, to develop multi-species tests (particularly in the field), to improve methods for risk assessment, and to develop options for mitigating risks. Large scale, long-term trans-disciplinary research of different farming systems is needed, particularly in North America, to integrate and better evaluate ecological, agronomic, and socio-economic costs and benefits of agricultural herbicide use in temperate landscapes.

A Review and Synthesis of Habitat Use by Breeding Birds in Agricultural Landscapes of Iowa

Existing information on bird species composition, abundance and nesting sta- tus during the breeding season (May through July) was compiled for habitats characteristic of the agricultural landscapes of Iowa. Data were derived from 60 sources for 144 bird species in 20 habitats. Total numbers of breeding bird species were highest in floodplain forest (107 species) and upland forest (85), and lowest in small grains (31) and herbaceous fencerows (27). Species abundances were standardized and categorized on a scale from 0 (absent) through 5 (very abundant with >250 individual birds/census count/100 ha). Bird species abundances are lowest in some agricultural habitats (e.g., tilled row crops and small grains) and highest in narrow, strip-cover habitats (e.g., railroad rights-of-way, wooded fencerows and farmstead shelterbelts). Species abundance patterns in natural habitats (forest, marsh and prairie) are intermediate between those in agricultural and strip-cover habitats. Twenty-five species occurred only in forest habitats and 14 only in marshes. Other species selectively (through not exclusively) use tilled row crop, grassland or wooded habitats. Principal com- ponents analysis was used to assess the relative similarities in use of the 20 habitats by the assemblage of breeding birds in Iowa. Predicted numbers of nesting species increased from 18 to 93 over four landscape scenarios representing a progression from an intensively farmed row-crop monoculture to a diverse mosaic of crop and noncrop habitats. Although laborious, the approach developed in our study has been useful for standardizing and synthesizing a diverse literature in efforts to conduct ecological risk assessments for farmland birds. It can also provide valuable baseline data for landscape-level research.

Birds on organic and conventional farms in Ontario: partitioning effects of habitat and practices on species composition and abundance

Population declines of farmland birds over recent decades in Europe, Canada and the USA have been attributed to more intensive agricultural management. We counted birds during the 1990 breeding season on 72 field sites in southern Ontario, Canada, paired between 10 organic and 10 conventional farms for local habitat to enhance our ability to detect effects of agricultural practices. Of 68 species recorded, 58 were on organic sites, 59 on conventional. Species richness and total abundance were significantly greater on organic than conventional sites based on log-linear regression. Of 43 species analyzed with log-linear regression, eight (18.6%) were significantly (P<0.05) more abundant on organic than conventional sites and four (9.3%) approached significance (0.05<P<0.10). Eight of these 12 species had negative population trends for 1967–1998 Breeding Bird Surveys (BBS) in this region. Two of the 43 species analyzed (4.7%) were significantly more abundant on conventional than organic sites and three (7.0%) approached significance. Two of these five species had negative BBS population trends. A canonical correspondence analysis (CCA) of 13 practices and 13 habitat variables explained 44% of total variation (TV) accounted for in a detrended correspondence analysis of bird species composition and abundance. Practices contributed 23.7% of TV, habitat 26%; habitat and practices shared 5.7% with each other and 12% with farm ownership (i.e. clustering of field sites within farms). CCA ordinations indicated considerable mixing of organic and conventional sites across a gradient from sites with many birds species associated with greater habitat heterogeneity and more pasture, winter grain, farmstead and other non-crop habitats (hedgerow, woodland) to sites with few bird species associated with larger fields, more rowcrop and spring grain, more passes and tilling, and use of herbicides and chemical fertilizers. Our results re-emphasize the importance of non-crop habitats, more permanent crop cover, and less intensive management practices to the conservation of avian biodiversity on farmland.

Assessing alternative futures for agriculture in Iowa, U.S.A

The contributions of current agricultural practices to environmental degradation and the social problems facing agricultural regions are well known. However, landscape-scale alternatives to current trends have not been fully explored nor their potential impacts quantified. To address this research need, our interdisciplinary team designed three alternative future scenarios for two watersheds in Iowa, USA, and used spatially-explicit models to evaluate the potential consequences of changes in farmland management. This paper summarizes and integrates the results of this interdisciplinary research project into an assessment of the designed alternatives intended to improve our understanding of landscape ecology in agricultural ecosystems and to inform agricultural policy. Scenario futures were digitized into a Geographic Information System (GIS), visualized with maps and simulated images, and evaluated for multiple endpoints to assess impacts of land use change on water quality, social and economic goals, and native flora and fauna. The Biodiversity scenario, targeting restoration of indigenous biodiversity, ranked higher than the current landscape for all endpoints (biodiversity, water quality, farmer preference, and profitability). The Biodiversity scenario ranked higher than the Production scenario (which focused on profitable agricultural production) in all endpoints but profitability, for which the two scenarios scored similarly, and also ranked higher than the Water Quality scenario in all endpoints except water quality. The Water Quality scenario, which targeted improvement in water quality, ranked highest of all landscapes in potential water quality and higher than the current landscape and the Production scenario in all but profitability. Our results indicate that innovative agricultural practices targeting environmental improvements may be acceptable to farmers and could substantially reduce the environmental impacts of agriculture in this region.

Toxicity of hexazinone and diquat to green algae, diatoms, cyanobacteria and duckweed

Abstract Hexazinone and diquat are two broad-spectrum contact herbicides used in a variety of crop and non-crop applications. Both pesticides are highly water soluble and persistent in the aquatic system. Hexazinone is mobile in soil and, thus, the potential for leaching into ground water and for overland runoff into surface water is high; diquat, however, is rapidly bound by soil and sediment to a biologically inactive form, at least temporarily. Toxicity to green algae (two species), diatoms (two species) and cyanobacteria (five species) was determined using inhibition of 14 C uptake. Toxicity to the floating vascular plant, duckweed, was tested by measuring seven-day growth inhibition. Test organisms exhibited large differences in sensitivity to both herbicides. The green algae, diatoms, and duckweed (all eukaryotes) were more sensitive to hexazinone than were cyanobacteria (prokaryotes). Mean concentrations at which 50% inhibition occurred in these groups were 0.01 (green algae), 0.05 (diatoms), 0.07 (duckweed), and 0.6 (cyanobacteria) mg hexazinone per litre, respectively. In contrast, green algae were comparatively tolerant of diquat (EC 50 values approximately 0.6 mg l −1 ), while the cyanobacteria and diatoms were much more sensitive (mean EC 50 values of 0.074 and 0.079 mg diquat per litre). Duckweed showed the greatest sensitivity to diquat, with 50% inhibition of growth occurring at 0.004 mg l −1 . That some non-target aquatic plants are susceptible to diquat toxicity at less than 0.01 mg l −1 is significant, as most methods of diquat analysis have minimum detection limits of 0.01 to 0.05 mg l −1 . Therefore, algae and vascular aquatic plants may suffer phytotoxic effects in a contaminated water body even when diquat is undetectable chemically. Differential sensitivity to herbicide contaminants among taxonomic groups of plants may have ecological consequences. Cyanobacteria may produce neuro- and hepato-toxins and constitute a poor food resource for higher trophic levels relative to the other organisms tested. Contamination of surface water with hexazinone may degrade water quality for wildlife, both by causing food reduction and habitat loss through inhibition of green algae, diatoms and macrophytes, and by allowing the proliferation of cyanobacteria. Varying responses among the different test algae to the two herbicides under study indicated that a wide taxonomic range of test species is necessary in evaluating the impacts of contaminants in aquatic systems.

Assessing effects of agriculture on terrestrial wildlife: developing a hierarchical approach for the US EPA

Abstract Serious concerns exist about environmental and ecological degradation from modern agriculture. In response, the US Environmental Protection Agency (EPA) and the US Department of Agriculture have established cooperative research programs in the midwestern USA to evaluate effects of different landscape structures and farming practices on crop yield, movement of agrichemicals, water and soil quality, and biodiversity. This paper develops the hierarchical approach for those efforts particularly in relation to wild plants and animals (invertebrates, birds, small mammals) in terrestrial habitats. The importance of considering different levels of biological organization and types of agricultural Stressors over a hierarchy of spatial and temporal scales is developed and illustrated by studies from North America and Europe. EPA studies of farmland wildlife in the Midwest are used to illustrate an application of the hierarchical approach. Those efforts would be improved by more regionally specific information on effects for a greater variety of taxa and over a broader range of biological organization. Metapopulation dynamics also need study. More detailed studies are required to evaluate specific, alternative within-field management practices, land set-aside schemes, and habitat restoration or enhancement options. Development and linkage of GIS and spatially explicit population models would help develop, evaluate and communicate future scenarios. An opportunity exists in the Midwest programs to compare biological patterns at population, community and landscape levels with assessments of ecosystem processes over a hierarchy of spatio-temporal scales. The potential also exists to develop future scenarios which integrate across ecological, socio-political and economic perspectives. To accomplish this, a more inclusive and consultative approach is required. Changes in existing institutional processes and frameworks are likely required to promote the broad, integrated, transdisciplinary approaches needed for more effective planning, research and management of agricultural landscapes.

Influence of landscape composition on bird use of rowcrop fields

We evaluated the influence of landscape composition on bird use of rowcrop (corn and soybean) fields in 6 watersheds in Iowa from mid-May to late July 1993 and 1994. We counted birds within 50-m-radius circular plots positioned randomly within rowcrop fields and determined coverages for 21 habitats within 800-m-radius circles centered on each bird census plot. We evaluated the relationships between bird abundances in rowcrop fields and the habitat coverages in the landscape by using 2 multivariate procedures. We derived 3 landscape scenarios from a cluster analysis of the original habitat variables; the abundances of 7 bird species differed significantly among the 3 scenarios. Species abundances in rowcrop fields were greater in landscapes with more grassland block-cover and/or more wooded block-cover and strip-cover. Principal component analysis illustrated the responses of bird species to landscape composition; species responses depended upon the relative use (ranging from resident to occasional) that the birds made of the rowcrop fields. Habitat selection and use in birds is a multiscale phenomenon, and the landscape context should be considered when evaluating bird use of rowcrops.

Planning Alternative Future Landscapes in Oregon: Evaluating Effects on Water Quality and Biodiversity

The development of spatially explicit landscape analyses is a principal activity in research on the relationships between human activities and changes occurring in natural systems. Using geographical information systems and related tools we produced digital and paper representations depicting the past, present, and potential future conditions of a 320 km2 watershed in western Oregon. These tools were used to identify trends over space and time in human occupancy and natural resources. Based on a set of values and desired future conditions developed by working with citizen groups, digital representations of the alternative future landscapes were evaluated for their effects on water quality and biodiversity using hydrological and ecological effects models. The water quality evaluative model, a non-point pollutant source geographic information system model, simulated storm events based on field data to calculate pollutant loads across the five alternative futures, the present, and the past. The biodiversity evaluative model measured the change in species richness and potential habitat area for breeding species in each alternative future and in the past and compared these data to the present. Results from the water quality model show increases in the volume of surface water runoff and total suspended solids under the development-oriented futures in catchments undergoing significantly increased residential development or having a high percentage of area in erosive soils on steep slopes. Results from the biodiversity model show that all native species have at least some habitat in all alternative futures. If land use trends in the watershed continue unchanged or become more highly developed, there will be an increased risk to abundance of extant native species. The set of species at risk in the development-oriented futures differs significantly in composition and is placed at risk at a higher rate than in the past, suggesting that the kinds of habitat changes to date differ from those envisioned in the alternative futures.

Farmland birds in southern Ontario: field use, activity patterns and vulnerability to pesticide use

Abstract The use of cropfields by birds is largely unknown in southern Canada and consequently the risk incurred by pesticide use on bird populations cannot be adequately characterised. The activity patterns and relative interior to edge use of bird species were examined for four crops in southern Ontario to assess the susceptibility of different species to pesticide use. Altogether 138 species were identified in the four crops over the 2 year period but only 25 species were recorded during 50% of visits in at least 1 month: 14 in corn (Zea mays L.), 16 in soybean (Glycine max L. Merr.), 14 in apple (Malus spp.) orchards and eight in vineyards (Vitis spp.). Territorial behaviour was an important activity for several species from May through July in the four crops. Nesting was confirmed in May, June and July for most species, with the exception of American Goldfinch Carduelis tristis, Chipping Sparrow Spizella passerina and Cedar Waxwing Bombycilla cedrorum which nested in August/September. Foraging was the most important activity for most species in all months (7/10 species in May, 6/8 species in June, 4/8 species in July, 5/8 August/September). Few fledgling young were observed. Most species used field edges consistently more often than expected in corn and soybean fields, according to the edge/interior ratio, Yellow Warbler Dendroica petechia being the exception. In apple orchards, relatively few species differentiated between edge and interior. Based on their frequency of occurrence (>50%), behaviour and temporal coincidence with pesticide applications, 13 species were considered most at risk: Killdeer Charadrius vociferus, Horned Lark Eremophila alpestris, American Crow Corvus brachyrhynchos, American Robin Turdus migratorius, European Starling Sturnus vulgaris, Chipping Sparrow, Vesper Sparrow Pooecetes gramineus, Savannah Sparrow Passerculus sandwichensis, Song Sparrow Melospiza melodia, Red-winged Blackbird Agelaius phoeniceus, Common Grackle Quiscalus quiscala, Brown-headed Cowbird Molothrus ater and Barn Swallow Hirundo rustica. The latter species, because of its foraging habit, is less likely to be exposed to pesticides. This study was important to identify focal species that can be used for detailed investigations on exposure to pesticides.