Ecology and Conservation of Dragonflies and Damselflies
Dragonflies and damselflies play key roles in both terrestrial and aquatic habitats. They are predators as both nymphs and adults, feeding on a variety of prey including nuisance species such as mosquitoes and biting flies. Nymphs can be top predators in fishless wetlands and help structure the wetland community. Dragonfly and damselfly nymphs in turn are an essential food resource for fish and amphibians, and adults are eaten by upland predators such as birds, bats, lizards, and spiders. They can be indicators of different biotypes and habitats, and have been used as tools to assess the biological health of aquatic habitats and to detect levels of heavy metals such as mercury. They are also considered model organisms to assess the effects of global climate change.
Conservation of Species and Their Habitats
Despite their significant ecological importance in a variety of ecosystems, their reliance on aquatic habitats puts the survival of dragonflies and damselflies at risk, as freshwater ecosystems have experienced a severe decline and degradation worldwide. In less than 400 years from the time of European settlement, the conterminous United States lost more than half of the 221 million acres of wetlands that existed in the 1600s, as draining and filling these environments made way for increased settlement, industry, and farming. Managing wetlands to meet the needs of both wildlife and humans continues to be a struggle, and although protection and restoration efforts have increased, wetlands and other aquatic habitats still suffer from water quality issues. Many rivers and streams in the US are impacted by industrial and agricultural pollution, with poor habitat condition and excess nitrogen and phosphorous input responsible for the majority of water quality issues. In a 2008-2009 national river and stream assessment conducted by the Environmental Protection Agency (EPA), 55% of the nation’s river and stream miles were designated as poor habitat, i.e. unable to support healthy populations of aquatic life. In 2013 a total of 42,721 waters
(including over 520,000 river miles) nationwide were designated as impaired under the Clean Water Act, and whiles states have a mandate to remediate the conditions that caused the impairment and subsequent listing, multiple stressors continue to degrade these waterways. Three of the top water quality stressors for the nation’s rivers and streams are pathogens (primarily fecal coliform pathogens composed of Escherichia coli
]), nutrients (primarily nitrogen and phosphorous), and heavy metals (primarily mercury, iron, and aluminum).
Continuing degradation and loss of aquatic habitats results in fragmentation of freshwater systems and decreases habitat quality and connectivity. While much work has been done to protect and restore wetlands, studies have shown that created wetlands and ponds can also provide crucial habitat, especially in urban areas. Urban pond creation is on the rise; a 2011 EPA report found an increase in urban pond creation of 18% from 2004 to 2009. Creation of pond habitat on both private and public lands can support ecosystem connectivity for wildlife and provide urban refuges for a diversity of terrestrial and aquatic species.
With at least 20% of all described odonate species in North America considered to be at risk, the MDP and Xerces are working to raise awareness about threats to these animals and increase the quality and quantity of the habitats on which they rely. We hope to work with individual states to address gaps in dragonfly and damselfly species covered under the State Wildlife Action Plans (SWAPs) to gain protection for vulnerable species. The goal of SWAPs is to prevent species from becoming endangered or declining to levels where recovery is unlikely; species designated in SWAPs as Species of Greatest Conservation Need (SGCN) receive targeted conservation attention. Insects and other invertebrates are often neglected in mainstream conservation efforts because they are perceived as non-charismatic and are often understudied and/or their important ecological roles are not fully known or appreciated. Although nearly two-thirds of U.S. Odonata species were appointed as SGCN overall in a 2010 assessment of SWAPs, over half the states neglected to assign dragonfly SGCN, damselfly SGCN, or both. By working at the state level, the MDP and Xerces will be able to determine if there are dragonfly or damselfly species that are in need of conservation attention that are not being considered under these plans, and to advocate for their inclusion and conservation.
Working to gain protection of sensitive and at-risk odonate species is an important step to ensure these species do not decline to a level where recovery is impossible. Currently, only seven species of odonates are listed as endangered under the US Endangered Species Act (see links below for more information), but there are many more in need of conservation attention. Destruction and degradation of aquatic habitats as well as pollutants and introduced species are all leading factors in the loss and imperilment of odonates, and the continued survival of even common odonate species cannot be taken for granted. As conservationist Rosalie Edge said, “The time to protect a species is while it is still common”.
To learn more about creating pond habitat in your own backyard, check out the new Backyard Pond Habitat Guidelines: Create Habitat to Attract Dragonflies and Damselflies.
For more information, including how to participate in volunteer efforts to help researchers better understand dragonfly life history and their migration in North America, please visit: www.migratorydragonflypartnership.org.
Species Listed Under the U.S. Endangered Species Act