Transcript Slide 1
Talk will be available at Lab Website Google: Skelly Yale Global Amphibian Decline Take Home Points • Upland Conversion Eliminates Amphibian Populations • Isolation Fosters Extinction • Most Amphibians Are Specialists – Successful conservation requires a diversity of dynamic wetlands Context Matters. Yale Forest Tolland Manchester 0.3 inds / ha* 1.3 inds / ha 7.8 inds / ha 85% Forested 78% Forested 37% Forested 5% Impervious 8% Impervious 20% Impervious Species Disappear from Developed Wetlands Lost Diversity Across 60 Connecticut Wetlands Species per Wetland 6 5 4 3 2 1 0 Undeveloped Suburban Urban Landscape Skelly Unpublished Land Conversion: Wetland Size & Isolation Gibbs 2000 Land Conversion: Wetland Isolation Gibbs 2000 Land Conversion: Wetland Isolation Gibbs 2000 Gibbs 2000 Fragmentation: ‘Rural’ to Urban Transect 10 x 2 km Orange, CT 295 People/sq km Milford, CT 846 People/sq km Gibbs 1998 Fragmentation: ‘Rural’ to Urban Gibbs 1998 Fragmentation Leads to Local Extinction Species Loss In Intact Forest Patches Species Differ Gibbs 1998 Species are frequently missing from vernal ponds in deforested landscapes % of ponds occupied by spotted salamanders is higher when uplands are intact forest Homan et al. 2004 Isolated Wetlands are less likely to have persistent amphibian populations Isolation [m] 600 500 400 300 200 100 0 Never Invaded Extinct Stable Population Status Skelly et al. 1999 Whole Pond Experiment: Yale-Myers Forest Manipulated canopy in 6 wetlands in late 2001 then monitor population & community Responses At each wetland: ca. 25 overstory stems removed on S upland Canopy & Temperature Open 19 Closed o C 16 13 10 0.0 0.2 0.4 0.6 GSF 0.8 1.0 Reduced Canopy Tends to Increase Number of Species 6 5 Number of Species Following Cut in late 2001, new species have tended to move into Cut ponds. 4 Control Cut 3 2 1 0 2001 2002 2003 2004 2005 2006 Skelly Unpublished Altered Canopy Does Not Affect Wood Frog Abundance 300 250 Egg Masses Following Cut in late 2001, wood frogs have remained abundant 350 200 150 100 50 0 2002 2003 2004 2005 2006 2007 Skelly Unpublished Spotted Salamanders May be Even More Abundant with Altered Canopy 12 10 Egg Masses per Min Following Cut in late 2001, spotted salamanders may have Increased. 14 8 Control Cut 6 4 2 0 2002 2003 2004 2005 2006 2007 Skelly Unpublished Amphibians as Canopy Specialists Generalist – Few Species Threshold – Most Species Most species that can tolerate low light can occupy more wetlands % Wetlands Present 100 80 60 40 20 0 0 0.2 0.4 0.6 Average Light Level (GSF) Data for 8 Species 0.8 1 No single wetland type provides habitat for all amphibian species Canopy Generalist Spotted Salamander % Wetlands Present 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 1 Average Light Level (GSF) Marbled Salamander Closed Canopy Specialist American Toad Open Canopy Specialist How can we conserve Wetland Dwellers? • Protect Wetland and Upland Units • Develop Proactive Landscape Level Plans • Avoid Use of Mitigated Wetlands – Bigger is not better – Stormwater catchments are typically poor habitats • Allow/Foster Wetland Dynamics – Wetland Diversity in Space and Time – Beaver – Selective Cutting Take Home Points • Upland Conversion Eliminates Amphibian Populations • Isolation Fosters Extinction • Most Amphibians Are Specialists – Need a diversity of dynamic wetlands Context Matters. Amazon.com Sales Rank: #202,658 References • Gibbs JP 1998. Distribution of woodland amphibians along a forest fragmentation gradient Landscape Ecology 13: 263-268. • Gibbs JP 2000. Wetland loss and biodiversity conservation Conservation Biology 14: 314-317. • Halverson, M. A., D. K. Skelly, J. M. Kiesecker, and L. K. Freidenburg. 2003. Forest mediated light regime linked to amphibian distribution and performance. Oecologia 134:360-364. • Semlitsch RD 2000. Principles for management of aquatic-breeding amphibians Journal of Wildlife Management 64: 615-631. • Semlitsch RD, Bodie JR 2003. Biological criteria for buffer zones around wetlands and riparian habitats for amphibians and reptiles Conservation Biology 17: 1219-1228. • Semlitsch, R. D. and D. K. Skelly. 2007. Ecology and conservation of pool breeding amphibians. Pages 127-148 in Vernal Pools: Ecology and Conservation of Seasonal Wetlands in Northeastern North America (A. Calhoun and P. deMaynadier, Editors). CRC Press. ISBN 0849336759 • Skelly, D. K., E. E. Werner, and S. A. Cortwright. 1999. Long-term distributional dynamics of a Michigan amphibian assemblage. Ecology 80:2326-2337. • Skelly, D. K., M.A. Halverson, L. K. Freidenburg, and M. C. Urban. 2005. Canopy and amphibian biodiversity in forested wetlands. Wetland Ecology & Management. in press.