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Popular Herbicide Kills Tadpoles !! “Current application rates for the glyphosate formulation Roundup are highly lethal to many amphibian species.”Relyea,

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Presentation on theme: "Popular Herbicide Kills Tadpoles !! “Current application rates for the glyphosate formulation Roundup are highly lethal to many amphibian species.”Relyea,"— Presentation transcript:

1 Popular Herbicide Kills Tadpoles !! “Current application rates for the glyphosate formulation Roundup are highly lethal to many amphibian species.”Relyea, R Ecological Applications: 15:618–627. The popular herbicide Roundup is widely used to kill weeds, but a new study suggests it may also kill tadpoles in the wild. The findings could, in part, explain global amphibian declines “We contend that the application rates and resultant aqueous exposure concentrations used in this experiment are quite atypical of those associated with the dominant uses of glyphosate formulations in agricultre, forestry and industrial sectors.” Thompson et al Ecological Applications 16:

2 Why is this issue important to Canadian Forestry? Glyphosate is the dominant herbicide used in Canadian forestry Ontario is the largest single provincial user, majority in the North Aerial applications may result in contamination of forest wetlands Forest wetlands are critical habitat for many amphibian species

3 A Close Up Look - Potential Risk of Glyphosate Use on Amphibians -

4 Control of Competing Vegetation in Forestry Equivalent to Weeding Your Home Garden  Managing competing vegetation is essential to effective forest regeneration particularly on highly productive sites  Ineffective management leads to significant loss of conifer on the landscape and seriously erodes our international market niche and economic benefits  Managing competing vegetation is essential to effective forest regeneration particularly on highly productive sites  Ineffective management leads to significant loss of conifer on the landscape and seriously erodes our international market niche and economic benefits

5 Silvicultural Herbicide Use Patterns Vision® (glyphosate) controls more than 90% of the national market Total area treated with herbicide ~ 200 K ha annually  ONT is the major user accounting for ha annually

6 Operational Background 100,000 ha of Ontario forests treated annually glyphosate (>90%), predominantly by air Loss of aerial herbicide capability 4X increase in tending cost 40% reduction in productive forest land base (Wagner 1992) Demand for continuous improvements PUBLIC (environmental concerns) CLIENT (sustainability & environmentally acceptable practices) FOREST INDUSTRY (operational cost-effectiveness - $$$$)

7 Glyphosate Based Herbicides Roundup ®, Roundup Original ®, Vision ®, WeatherMax ®, VisionMax ®, Touchdown ®, Roundup Biactive ®, Catena ® Dominant herbicide in agriculture and forestry worldwide >$14 million USD Glyphosate inhibits AAA biosynthesis by blocking a specific synthase enzyme Target pathway exists in plants & microbes but not in higher animals POEA surfactant is primary toxicant - general narcosis Both glyphosate and POEA bind strongly to organic substrates Neither glyphosate nor POEA are persistent in shallow lentic aquatic systems containing sediments Glyphosate DT50 = 4.2 days Thompson et al. (unpublished) POEA DT50 = days Wang et al 2005 Glyphosate AMPA

8 Herbicide Applications in Northern Ontario Are Typically Made by Air Potential for direct or indirect input into small forest wetlands which are not mapped or visible from the air

9 Forest Wetlands ubiquitous in eastern Canadian forest landscapes critical habitat for many species including native amphibians susceptible to pesticide contamination (overspray, drift, runoff)

10 Tiered Approach to Ecotoxicological Research Standard Laboratory Toxicity Testing In-Situ Aquatic Enclosures Operational Biomonitoring Increasing Environmental Realism,/ Ecological Relevance/Extrapolative Certainty Decreasing Experimental Control/ Replication/Comparability

11 PEC Comparative Lab Toxicity - Amphibians Edginton et al ET&C 23:

12 Most Sensitive Aquatic Species Toxicity Threshold Values for glyphosate Vision Toxicity EndpointValue (mg a.e./L) Study Type Reference IC 25 M. sibiricum (Plant) 0.6Lab Roshon et al LC 10 R. pipiens (amphibian larvae) 0.8Lab Edginton et al LC 10 R. clamitans (amphibian larvae) 1.2Field Wojtaszek et al 2004 NOEC O. mykiss (fish) 0.8Lab Solomon & Thompson 2003

13 Glyphosate Concentration (µg a.e./L) Percent rank of LC 50 Values All aquatic organisms Fish Amphibia Species Sensitivity Distributions (SSDs) For Aquatic Organisms Exposed to Roundup ® or Vision ® Formulations Solomon and Thompson (In prep) Data from: US EPA ECOTOX data-base {USEPA, 2001} Amphibians 1100 Fish 1736

14 Relyea Study (Relyea Ecol. Appl. 15: ) Mesocosm Type: 1200 L cattle tanks ammended with 25 different species Treatment: Roundup Weed & Grass Killer Concentrate Test Conc: 3.1 mg a.e./L Amphibians: (5 spp. 10 larvae of each/tank) R. sylvatica, R. pipiens, H. versicolor, P. crucifer, A. maculatum, B. americanus Sediments: None but 300 g leaf material/tank Macrophytes: None pH: not reported Result: Complete mortality of R. pipiens & H. versicolor, 98% mortality of R. sylvatica following 14 day exposure period.

15 Wojtaszek Study (Wojtaszek et al ET&C. 23: ) In Situ Enclosures: 2 Different Wetlands Treatment: Vision concentrations from 0.29 to 14.3 mg a.e./L Amphibians: R. pipiens, R. clamitans (10 larvae of each sp. caged/enclosure) Test Conditions: Natural Sediments & Macrophytes pH: D.O. ~ 8 ppm Depth: 1 or 2 m Results: No significant mortality, avoidance response or growth < 1.43 mg a.e./L 96 hr LC 10 = 1.2 to 7.3 mg a.e./L depending upon site and species

16 Operational Monitoring Studies monitoring in 51 different wetlands (overprayed, adjacent or buffered) aerial applications of glyphosate (Vision) avg 1.9 kg a.e./ha In-situ biological monitoring with caged larvae (green & leopard frogs)

17 Environmental Exposures vs Toxicity Threshold NOEC or LC10 >2 x >4 x > 26 x Probability of exposure to detectable levels (0.01 mg a.e./L) of glyphosate (12%)(45%)(83%)

18 Biomonitoring Results control & buffer mortality for R. clamitans NSD (p=0.05) in mean mortality for either species Trends in mean mortality did not follow a concentration-response pattern No significant (p=0.05) regression relationship between acute mortality & exposure concentration for either species results consistent with tier III concentration-response relationships Mortality at 48 h Exposure

19 Comparative Rates & Exposure Concentrations UseApplic. Rate (kg a.e./ha) RatioAq. Conc. (mg a.e./L) Sites (Period) Reference Home & Garden (Relyea Test) Relyea 2005 Amphibian Tox. 96 h LC 10 (lab) 96 h LC 10 (Field) 14d Mort/Growth Edginton et al Wojtaszek et al Forestry (Conifer Release) 2.141/6th<0.55* Over-sprayed 24 (2 yrs) Thompson et al Agriculture. (Typic USA/CDN) 1.601/8th<0.01 * Amphib sites 32 (2 yrs) Struger & Thompson (unpublished) Orchards (Netherlands) N/A <0.023*21 (5 yrs) ZHEW (2002) as cited in Horth et al Roadside (Typical USA) 1.071/12th<0.005N/AWood 2001 * Upper 99th centile confidence limits

20 Major Scientific Reviews Fate and effects of Glyphosate in the Environment 1. Rueppel et al Ghassemi, M. et al USDA-FS Grossbard E. & D. Atkinson (Eds) USDA 1984, 1989, 1992, 1996, Servizi et al Environment Canada USEPA Newton et al WHO - International Program on Chemical Safety Sullivan and Sullivan Roshon, R.D. et al Environment Canada Giesy, J. P. et al Williams, G.M. et al Solomon, K.R. & D.G. Thompson Sullivan and Sullivan 2005 (in press) – soil organisms 18. Solomon, K.R. & D.G. Thompson 2006 (in prep) – amphibians

21 Take Home Points Larval amphibians are very sensitive to GLYPH formulations containing POEA Concentrations even in directly over-sprayed forest wetlands are typically much lower than NOEC or LC10 toxicity threshold estimates Typical real world exposure concentrations are unlikely to pose a significant risk to sensitive larval amphibians


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