Small wetlands are critical for safeguarding rare and threatened plant species

Abstract

Question Rare and threatened species are a common focus of natural area protection, but selecting sites to protect them must be balanced against other conservation objectives. Using a series of wetlands as a case study, we ask: (i) will protecting sites based on species rarity capture all critical community types; (ii) do rare plant species occur in rare environments; and (iii) will safeguarding large wetlands protect taxonomic and functional richness of rare and threatened species? Location Southern New Zealand. Methods We used lists of vascular plant species from 118 wetlands (66 fens, 35 bogs and 17 marshes). The resulting species lists included 29 rare and threatened species. Nine functional attributes of the rare and threatened species were compiled. Species assemblages were ordinated using non‐metric multidimensional scaling. Permutational multivariate ANOVA tested for a difference in assemblages between wetlands with or without rare and threatened species. Wetlands were classified according to a rare environment scheme. SLOSS (single‐large‐or‐several‐small) accumulation curves determined whether species and functional richness of rare and threatened species were best captured by groups of small or large wetlands. Results Wetlands with rare and threatened species supported species assemblages, which were different from those without rare or threatened plant species. Rare and threatened species were not associated with rare environments. The presence or richness of rare and threatened species was not associated with wetland size. SLOSS analyses revealed that small wetlands were critical for capturing rare and threatened species and their functional richness. Conclusions Prioritizing wetlands with rare and threatened plant species will not meet other conservation objectives, such as the preservation of all critical community types, rare environments or large wetlands. Networks of small wetlands will be necessary to safeguard rare and threatened plant species. Complementary objectives targeted at wetlands of varying size will be necessary to protect the full range of biodiversity and ecosystem services that wetlands offer.

Why do several small patches hold more species than few large patches?

“…In fact, many studies have found little or no relationship between the degree of nestedness and SLOSS (Berglund & Jonsson, ; Cook, ; Cutler, ; McLain & Pratt, ; Peintinger, Bergamini, & Schmid, ; Simberloff & Martin, ). In addition, it appears that most systems are either not nested or only weakly nested by patch size (Acosta & Robertson, ; Dauber, Bengtsson, & Lenoir, ; Hokkanen, Kouki, & Komonen, ; Mohd‐Azlan & Lawes, ; Richardson et al, ; Rosch et al, ). This might be because species occurrence is not only affected by extinction, but is also affected by colonization (see Section ).…”

“…Thus, if sets of many small patches are more heterogeneous than sets of few large patches then we might find SS > SL. In fact this was the most common explanation provided by authors for their findings of SS > SL in my review of empirical SLOSS studies (Baz & Garcia Boyero, 1996;Dauber et al, 2006;Dzwonko & Loster, 1989;Game & Peterken, 1984;Magura, Ködöböcz, & Tόthmérész, 2001;Martínez-Sanz, Cenzano, Fernández-Aláez, & García-Criado, 2012;McNeil & Fairweather, 1993;Peintinger et al, 2003;Richardson et al, 2015;Saetersdahl, 1994;Seibold et al, 2017;Simberloff & Gotelli, 1984;Tscharntke, Steffan-Dewenter, Kruess, & Thies, 2002;Virolainen, Suomi, Suhonen, & Kuitunen, 1998).…”

Wetland Soil Carbon in a Watershed Context for the Prairie Pothole Region

“…Other factors alter SOC stocks in the PPR that were not addressed here (Johnson et al, 2005; Johnston, 2014). Headwater wetlands were small and often geographically isolated (Tiner, 2003), so excavation could damage ecosystems critical for safeguarding rare and threatened species (Richardson et al, 2015). Results of this study point to the importance of evaluating PPR wetland SOC, SOC turnover, and restoration in a watershed context.…”

Impaired Wetlands in a Damaged Landscape

“…Sequential deletion of drying wetlands truncates the end of the moisture gradient and causes what is known in fisheries science as a shifting baseline which undermines the ability to detect change. Furthermore, small wetlands are critical for conservation of rare plant species (Richardson et al 2014). Failure to monitor small and/or desiccating wetlands will undermine the ability to detect changes in rare plant biodiversity.…”