The role of botanic gardens and arboreta in restoring plants: From populations to ecosystems

Introduction We live at a time when the world’s natural areas are under continual assault; from invasive species, pollution, human use impacts and fragmentation, and climate-related natural disasters like drought, wildfire and flooding. Ecological restoration, the process of assisting the recovery of an ecosystem that has been degraded, damaged or destroyed (SER, 2004), is becoming ever more necessary to ensure that resilient ecological communities, including the biodiversity they support and the ecosystem services they provide, are maintained. The need for increased ecological restoration has been noted in numerous international policy documents including the Global Strategy for Plant Conservation, the Aichi Biodiversity Targets, the Millennium Ecosystem Assessment, and others. Worldwide, governments have already committed to restoring a staggering 3.5 million km² by 2030 (UN Climate Summit, 2014) in part to reach the United Nations’ target to restore 15 per cent of the world’s degraded ecosystems by 2020. Throughout the over 500-year history of botanic gardens and arboreta (hereafter botanic gardens or gardens), research has been an important part of their activities. Many botanic gardens were originally developed to curate collections in support of taxonomic research or the study of medicinal plants, and most maintain strong programmes in plant systematic and floristic work. In the past few decades, as scientists have recognised the extinction crisis facing us, the missions of many gardens have embraced conservation and restoration roles (Maunder et al., 2004a). As zoos have done for rare animals, gardens have developed ex situ conservation and breeding programmes to provide plant material for reintroduction and restoration. With core competencies in plant identification, taxonomy and ecology, as well as vast horticultural knowledge, botanic gardens are well positioned to provide expertise necessary for successful restoration projects. For example, the implementation of a restoration project requires the ecological understanding to know if a degraded site is likely to recover with proper management or whether it requires complete restoration. It requires knowledge of native plant distributions and plant community composition in order to develop appropriate seed mixes based on reference ecosystems. It requires understanding of conditions for seed dormancy break and plant establishment from seed. It requires being able to discern seedlings of native taxa from weeds. Botanic gardens have expertise in all of these areas.