It's a combination of factors ... not just increasing available lentic waters and beaver-cleared openings in stream channels. Beaver dams and ponds capture sediment that in turn supports herbaceous plants like sedges that many odes use as habitat. Beaver ponds, through succession, become sedge marshes and moist-soil meadows.The dams reduce impact of flash floods, hold water in the stream channel longer, and provide a buffer against the effects of drought. You can see the impact throughout the Southwest from beaver removal ... greater channel incision, reduced surface flows, and ultimately loss of surface water and the diversity of aquatic and palustrine microhabitats that odonates need.
A few of our Southwestern species (especially here in NM) that seem to rely on or benefit from beaver activity in montane areas include a couple of the same holarctic species mentioned in this publication:
James N. Stuart
jnstuart61 AT yahoo.com
"All calculations based on experience elsewhere fail in New Mexico" -- Lew Wallace, New Mexico Territorial Governor, 1878-81
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