A Rare Opportunity: A Case for Rare Plant Conservation at Matthaei Botanical Gardens & Nichols Arboretum

Abstract

The rate of biodiversity loss caused by humans has increased over the last century, and the current rates of species extinction are twice as high as the expected background extinction rates, creating what is known as the Sixth Mass Extinction (M.E.A., 2005, Ceballos et al., 2015). Not only are we seeing increases in biodiversity loss, but we are also experiencing biotic homogenization, where endemic species are lost to widespread species (McKinney & Lockwood, 1999). This loss in biodiversity can result in the removal of functional traits and functional groups of an ecosystem, leading to a loss of ecosystem resilience (Folke et al., 2004, Cardinale et al., 2012).Resilience, as Holling (1973) describes, is the ability of an ecosystem to absorb changes and still maintain its state and function. Furthermore, in the context of plant communities, increases in plant biodiversity are linked to decreases in plant pathogens and increases in wood production, resistance to plant invasion, carbon sequestration and storage, soil organic matter, and soil nutrient mineralization (Cardinale et al., 2012). Rare species contribute to plant biodiversity, and although they have been thought to play insignificant roles in ecosystem services (Dee et al., 2019), rare plants have been shown to be important in nutrient availability and cycling, providing critical resources to pollinators (Jolls et al., 2018), and preventing new species invasions (Lyons et al., 2005). Mouillot et al. (2013) found that rare species in alpine ecosystems provided important functional traits to support insects and that a rare tree species in French Guiana may be able to withstand increasing fire frequency and maintain forest function and structure in future climate states. In addition to ecosystem services, rare species provide important cultural services (Dee et al., 2019), an example being Michigan’s state wildflower, Dwarf Lake Iris (Iris lacustris), a Threatened species endemic to the Great Lakes Region. Despite their ecological and cultural importance a growing number of rare plant species face the threat of extinction. In response to the growing threat of extinction to plant species around the globe, the Convention on Biological Diversity (CBD) developed the Global Strategy for Plant Conservation (GSPC) in 2002 (Background and Consultations, n.d.). In fact, approximately 36.5% of all land plants are rare (Enquist et al., 2019). The United States and Michigan are not immune to plant extinction; one third of U.S. native flora is threatened, including 11-16% of tree species (Havens et al., 2014, Carrero et al., 2022), and in Michigan, approximately 24% (441) of native plant species are considered rare (i.e., Special Concern [114], Threatened [202], Endangered [78], or Extirpated [48]) (Michigan Flora Online, n.d.; Michigan's Rare Plants - Michigan Natural Features Inventory, n.d.). One of the goals of the GPSC to help address plant extinctions, is Target 8, which calls for “at least 75% of threatened plant species to be represented in ex-situ collections” and “at least 20% of those threatened species to be available for recovery and restoration programs by 2020.” Ex-situ conservation refers to conservation methods in which a species is conserved in a place other than where it naturally occurs (in-situ). While in-situ conservation or protecting species in their natural habitats is the ultimate goal of conservation, this approach is not without drawbacks. In general, in-situ conservation is more costly, and in an ecosystem approach to conservation, plant populations are still susceptible to natural disasters and anthropogenic threats, such as invasive species, pests, and climate change (Falk, 1990, Heywood & Iriondo, 2003, Li & Pritchard, 2009, Mounce et al., 2017, Soulé & Mills, 1992). To demonstrate the cost difference between in- and ex-situ conservation, it has been estimated that ex-situ seed conservation costs as little as 1% of that of in-situ conservation (Li & Pritchard, 2009). However, ex-situ conservation is not without its own issues. Specifically, ex-situ conservation efforts that involve cultivating plant species must deal with genetic drift, artificial selection, and in/outbreeding depression, all of which can render a collection useless as a source for conservation purposes (Volis & Blecher, 2010). Overall, however, botanical gardens and seed banks maintain samples of plant diversity that are believed to be lost from the wild, which has prevented or delayed extinctions for many species (Raven, 2004). Organizations such as botanical gardens are ideally situated to support both ex-situ and in-situ conservation efforts. Currently, botanic gardens are performing plant conservation with networks of botanic gardens facilitating the work (Havens et al., 2014). Botanical gardens having an active role in conservation is not new and can be traced back to the International Congresses for Nature Protection in 1923 and 1931 (Volis & Blecher, 2010). With infrastructure such as greenhouses and irrigation already in place and horticulturists with skills applicable for in-situ conservation, botanic gardens are ideal sites for plant conservation (Blackmore et al., 2011). Worldwide they host millions of visitors each year (Havens et al., 2006, Westwood et al., 2021, Blackmore et al., 2011), and they are sites of critically important research (see: Primack & Miller-Rushing, 2009, Norstog et al., 1986). Botanic gardens have also done significant research in understanding how plants will respond to climate change and have instituted citizen science programs that help monitor threatened species populations (Chen & Sun, 2018, Havens et al., 2006). Even though there is a history of botanical gardens having a role in plant conservation, Mounce et al. (2017) report that only 41% of all threatened species are accounted for in ex-situ collections and comprise only 10% of total collections. Additionally, Westwood et al. (2021) have argued that “gardens will not be able to achieve the results needed to avert the plant extinction crisis without a revolution in the way resources, funding, and public attention are 6 focused.” This indicates that there is still progress to be made in plant conservation at botanic gardens. Matthaei Botanical Gardens and Nichols Arboretum (MBGNA) is positioned perfectly to step into a role of rare plant conservation. The mission of MBGNA is as follows: “Matthaei Botanical Gardens and Nichols Arboretum is a transformative force for social and ecological resilience through the waters and lands we steward. We turn this commitment into action by: ● Positioning humans as active participants within the natural world and compelling the university community and our publics to negotiate the full complexity that entails ● Advancing partnerships, programs, user experience, and all that we steward to catalyze equity and justice in a radically changing world ● Emerging as University of Michigan’s premier partner for research, teaching, and public impact in sustainability, climate-forward practices, and biocultural diversity ● Promoting healthier communities, cultures, and ecosystems through active care and cultivation of the gardens, fields, natural habitats, and dynamic systems that sustain our world” Having a robust rare plant conservation program would enable MBGNA to fulfill its mission in promoting healthier ecosystems and advancing partnerships. In addition, across its four properties and conservatory, MBGNA holds approximately 93 species of plants that have legal protection or are species of special concern, which may need legal protection in the future. Despite this number of rare plants, MBGNA has no specific, focused program or person dedicated to the conservation of rare plants. The goals of this report are: 1) to outline reasons why it is possible for MBGNA to have such a program 2) to address what species MBGNA should initially focus on 3) to demonstrate what forms the conservation program could take 4) identify who the program could engage with.