AN APPEAL TO PROTECT AND RESTORE ...

In: Stream Restoration: Halting Disturbances,… Editor: Gillian D. Hayes and Timothy S. Flores

ISBN: 978-1-60876-450-1 © 2009 Nova Science Publishers, Inc.

Chapter 7

AN APPEAL TO PROTECT AND RESTORE EXPOSED RIVERINE SEDIMENTS (ERS) IN NORTH AMERICA Michael D. Ulyshen1 and Scott Horn2 1

Department of Entomology, Michigan State University, East Lansing, Michigan 48823 2 USDA Forest Service, 320 Green Street, Athens, Georgia 30602

ABSTRACT Exposed riverine sediments (ERS) are relatively un-vegetated deposits of gravel, sand, silt or some combination found within the stream channel. These habitats support diverse disturbance-adapted arthropod faunas, including both specialist and opportunistic species, and are therefore important in maintaining riparian biodiversity. Because ERS habitat heterogeneity is essential in maintaining diverse arthropod faunas, anthropogenic stream modifications that alter the complexity and hydrological regime of streams have detrimental effects. Many species in Europe have gone extinct, at least regionally, and many others have become highly threatened. Though less well studied, there are some troubling indications that North American ERS arthropods are facing a similar crisis. While restoring ERS habitats should be possible, the lack of previous survey data will make it difficult to monitor arthropod community recovery. Therefore, protecting ERS habitats from further degradation should be a top priority. Riparian habitats are becoming increasingly imperiled worldwide from anthropogenic modifications that include dams and levees, channelization, deforestation, erosion and sediment removal, to name a few. Of particular concern are exposed riverine sediments (ERS), relatively un-vegetated deposits of gravel, sand, silt or some combination found within the stream channel. Studies from Europe demonstrate that ERS support diverse disturbance-adapted arthropod faunas, including both specialist and opportunistic species, and are therefore important in maintaining riparian biodiversity. For example, an estimated 3.5% of all beetle species in Britain are ERS specialists [Sadler et al. 2004, and references therein]. In addition, ERS faunas are dominated by predators (e.g., ground beetles (Carabidae), rove beetles (Staphylinidae), spiders, etc.), many of which prey largely or exclusively on aquatic insects [Hering et al. 1997; Hering 1998; Paetzold et al. 2005], thereby performing the important function of linking aquatic and terrestrial food webs. While the importance of ERS has been well documented in Europe, research in other regions, including North America, is largely lacking. Here we

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Michael D. Ulyshen and Scott Horn review the current literature on arthropods and exposed riverine sediments for the purpose of raising awareness among researchers outside of Europe, particularly in North America, about these important habitats. A number of features vary among and within ERS, with important implications for arthropod diversity and community composition. Wider patches of ERS contain wider moisture and elevation gradients and support more species than smaller patches [Bates et al. 2007b]. The faunas of mid-channel patches (e.g., islands) likely differ from those of shoreline patches due to differences in accessibility as well as to differences in temperature and humidity (e.g., shoreline patches are often more shaded). ERS duration, determined by flood frequency, governs the extent to which plants become established, with significant effects on arthropod community composition [Eyre et al. 2001; Sadler et al. 2004; Lambeets et al. 2008]. Sediment type and particle size distribution are also important determinants of arthropod community composition [Eyre et al. 2001; Manderbach and Hering 2001], both varying among streams due to differences in geology and within streams due to differences in current velocity (Sadler et al. 2004). Andersen and Hanssen (2005) distinguish between “lithophilous” species on sites with stones and/or gravel and “psammophilous” species on sites consisting of pure sand. The finest sediments (i.e., silt) support distinct communities as well [Sadler et al. 2004; Lambeets et al. 2008]. Finally, dead wood and other plant material [Loeser et al. 2006] are common riparian features in many regions, further enhancing structural complexity and resource availability on ERS. Because ERS habitat heterogeneity is essential in maintaining diverse arthropod faunas, anthropogenic stream modifications that alter the complexity and hydrological regime of streams can be expected to have severe detrimental effects. Channelization (e.g., dredging, straightening) is perhaps the most damaging of all, virtually eliminating ERS from streams [Eyre et al. 2001]. Dams are also highly disruptive, flooding waterways upstream and simplifying flow patterns downstream, reducing ERS dynamism and promoting plant growth [Bonn et al. 2002; Sadler et al. 2004, and references therein]. Stream hydrology is particularly altered near hydroelectric plants [Paetzold et al. 2008]. By reducing stream flow, dams also result in increased silt deposition [Eyre et al. 2001]. Erosion and sediment extraction alter sediment type and particle size distribution. Deforestation changes shoreline temperature and humidity and affects inputs of wood and other plant material. Livestock trampling and defecation reduce ERS habitat quality in many regions [Sadler et al. 2004; Bates et al. 2007a]. Additional factors contributing to ERS degradation are urbanization, runoff pollutants, and recreational activities (e.g., allterrain vehicles). Unaltered streams are becoming increasingly rare around the world, yet few efforts have been made to assess the status of ERS arthropods in most regions. The available data from Europe, the best-studied region, are sobering, underscoring the vulnerability of this diverse fauna. Some species are already extinct, at least regionally, whereas many others have become highly imperiled [Andersen and Hanssen 2005]. For example, nearly 20% of the beetle species captured on ERS in Britain by Sadler et al. (2004) were of conservation concern. Though less well studied, there are some troubling indications that North American ERS arthropods are facing a similar crisis. For example, two tiger beetles (Carabidae: Cicindelinae) dependent on streamside sandbars, Cicindela hirticollis abrupta and Cicindela puritana, are presumably extinct and threatened, respectively, as a consequence of flow regulation [Omland 2002; Knisley and Fenster 2005]. Because few efforts have been made to inventory arthropods occurring on ERS in North America, little is known about community composition and even less about the conservation status of the constituent species. For example, in a recent survey of ground beetles on ERS in Georgia, the most frequently captured species by far, Brachinus janthinipennis, was not previously known from the state [Horn and Ulyshen 2009].

An Appeal to Protect and Restore Exposed Riverine Sediments (Ers) in North America 3 Few streams in North America remain unaltered. In the United States, for example, a country with over 80,000 dams and extensively degraded riparian forests, only 2% of rivers are considered “unimpacted” (Palmer et al. 2007 and sources therein). While extensive surveys are needed before conservations plans can be developed for North American ERS arthropods, steps should be taken in the meantime, when possible, to protect and restore ERS habitats. ERS are less complex than many imperiled ecosystems and should be less difficult to restore. However, while arthropods are disturbance-adapted and frequently exhibit high recolonization potential, some species are less resilient [Hering et al. 2004] and the lack of previous survey data will make it difficult to monitor arthropod community recovery. Consequently, protecting ERS habitats from further degradation should be a top priority.

REFERENCES Andersen, J & Hanssen, O (2005). Riparian beetles, a unique, but vulnerable element in the fauna of Fennoscandia. Biodiversity and Conservation 14, 3497-3524. Bates, AJ; Sadler, JP & Fowles, AP (2007a). Livestock trampling reduces the conservation value of beetle communities on high quality exposed riverine sediments. Biodiversity and Conservation 16, 1491-1509. Bates, AJ; Sadler, JP; Perry, JN & Fowles, AP (2007b). The microspatial distribution of beetles (Coleoptera) on exposed riverine sediments (ERS). European Journal of Entomology 104, 479-487. Bonn, A; Hagen, K, Wohlgemuth-Von Reiche, D (2002). The significance of flood regimes for carabid beetle and spider communities in riparian habitats- A comparison of three major rivers in Germany. River Research and Applications 18, 43-64. Eyre, MD; Luff, ML & Phillips, DA (2001). The ground beetles (Coleoptera: Carabidae) of exposed riverine sediments in Scotland and northern England. Biodiversity and Conservation 10, 403-426. Hering, D. (1998). Riparian beetles (Coleoptera) along a small stream in the Orgeon coast range and their interactions with the aquatic environment. The Coleopterists Bulletin 52, 161-170. Hering, D; Gerhard, M; Manderbach, R & Reich, M. (2004). Impact of a 100-year flood on vegetation, benthic invertebrates, riparian fauna and large woody debris standing stock in an alpine floodplain. River Research and Applications 20, 445-457. Hering, D & Plachter, H. (1997). Riparian ground beetles (Coleoptera, Carabidae) preying on aquatic invertebrates: a feeding strategy in alpine floodplains. Oecologia 111, 261-270. Horn, S & Ulyshen, MD (2009). The importance of streamside sandbars to ground beetle (Coleoptera, Carabidae) communities in a deciduous forest. Journal of Insect Conservation 13, 119-123. Knisley, CB & Fenster, MS (2005). Apparent extinction of the tiger beetle, Cicindela hirticollis abrupta (Coleoptera: Carabidae: Cicindelidae). Coleopterists Bulletin 59, 451458. Lambeets, K; Hendrickx, F; Vanacker, S; Van Looy, K; Maelfait, JP & Bonte, D (2008). Assemblage structure and conservation value of spiders and carabid beetles from restored lowland river banks. Biodiversity and Conservation 17, 3133-3148.

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Loeser, MR; McRae, BH; Howe, MM & Whitham, TG (2006). Litter hovels as havens for riparian spiders in an unregulated river. Wetlands 26, 13-19. Manderbach, R & Hering, D. (2001). Typology of riparian ground beetle communities (Coleoptera, Carabidae, Bembidion spec.) in central Europe and adjacent areas. Archiv fur Hydrobiologie 152, 583-608. Omland, KS. (2002). Larval habitat and reintroduction site selection for Cicindela puritana in Connecticut. Northeastern Naturalist 9, 433-450. Paetzold, A; Schubert, CJ & Tockner, K. (2005). Aquatic terrestrial linkages along a braidedriver: Riparian arthropods feeding on aquatic insects. Ecosystems 8, 748-759. Paetzold, A; Yoshimura, C & Tockner, K. (2008). Riparian arthropod responses to flow regulation and river channelization. Journal of Applied Ecology 45, 894-903. Palmer, M; Allan, JD; Meyer, J & Bernhardt, ES. (2007). River restoration in the TwentyFirst Century: data and experimental knowledge to inform future efforts. Restoration Ecology 15, 472-481. Sadler, JP; Bell, D & Fowles, A. (2004). The hydroecological controls and conservation value of beetles on exposed riverine sediments in England and Wales. Biological Conservation 118, 41-56.