Climate‐change impacts exacerbate conservation threats in island systems: New Zealand as a case study

Abstract

A lthough islands cover only ~5% of the global land area, they support ~20% of terrestrial plant and vertebrate species (Courchamp et al. 2014). Insular species are particularly vulnerable to extinction; one-third of critically endangered species and nearly two-thirds of recent extinctions consisted of species endemic to islands (Tershy et al. 2015), and these declines may have impacts on Indigenous peoples (Lyver et al. 2019). Several interacting factors contribute to this vulnerability, including invasions by non-native species and habitat loss (Simberloff et al. 2013). Island ecosystems are particularly susceptible to multiple climate-change factors, including rising sea level and loss of suitable climatic conditions (Courchamp et al. 2014), but conservation and restoration efforts rarely account for such interacting drivers of change (Parmesan et al. 2013). Understanding the effects of climate change on island ecosystems necessitates knowing how climate interacts with other ecologically influential processes (eg habitat loss, land transformation, invasive species). Here, we use the example of New Zealand to highlight interactions between changing climate and other threats to biodiversity, and stress the need to collect and maintain long-term datasets to improve strategies to mitigate climate-change effects. Lessons learned from New Zealand are relevant to islands (and potentially continental systems) elsewhere (Simberloff 2019), particularly with respect to the indirect and interactive effects of climate-change impacts. Although we focus on land-based ecosystems, we note that warming seas and ocean acidification are affecting marine systems in New Zealand's territorial waters, as well as elsewhere. Finally, we emphasize the need to work with Indigenous communities to improve the effectiveness of mitigation and adaptation approaches. New Zealand (also known by the Indigenous name Aotearoa) consists of three main islands, along with hundreds of smaller islands in rivers, lakes, and harbors, as well

Current knowledge and potential impacts of climate change on New Zealand’s biological heritage

“…Extreme flooding may also alter river morphology which may change habitat quality and availability (Death et al 2015). Measured impacts are summarised in Table 2, but substantial knowledge gaps remain, particularly when impacts are indirect and have complicated mechanisms (Macinnis-Ng et al 2021). New Zealand's freshwater biota is often described as depauperate with a high degree of habitat and trophic generalism owing to life-history evolution in geographic isolation and unpredictable, variable climatic conditions (Winterbourn et al 1981).…”

“…Similarly, the ability to migrate and disperse will largely affect how species can adapt to changing conditions, and this varies widely between species and systems in New Zealand (McDowall 2006). Meanwhile, many freshwater ecosystems are highly impacted by existing land-use change and water abstraction which will exacerbate future climate changes due to global warming (Robertson et al 2016;Macinnis-Ng et al 2021).…”

“…Details of changes in temperature, precipitation patterns, wind, storms, and other climate factors are expanded in regional modelling produced by Ministry for the Environment (2016) and Ministry for the Environment and Stats NZ (2020) with some additional context provided by Hopkins et al (2015). While considering past climates is important for understanding potential impacts of future climate change (McGlone et al 2010;McGlone & Walker 2011), we confine the scope of this review to current and future climate because interacting factors such as invasive species and habitat fragmentation were not a feature of past climates (Macinnis-Ng et al 2021).…”

Burn probability mapping of Moutohorā (Whale Island), Bay of Plenty, Aotearoa New Zealand

“…Islands such as Moutohorā with high conservation and cultural values, that also carry high burn probability relative to their area, even with management of human activity are likely to become under increased threat due to climate change (Towns et al 2012;Sothieson et al 2016;Macinnis-Ng et al 2021). Modelling and research that can produce and improve fire burn probability mapping will have increased value for conservation, resource and cultural site managers.…”

Sticking around: plant persistence strategies on edaphic islands

“…These are “natural laboratories ” (Warren et al, 2015; Whittaker et al, 2017) and suitable models to examine persistence strategies because plants with limited dispersal on steadily isolated islands tend to exhibit adaptive strategies to successfully survive (Cody & Overton, 1996; Conti et al, 2021; Ottaviani et al, 2020a). At the same time, insular systems are particularly vulnerable to species extinctions linked to environmental changes (Courchamp et al, 2014; Macinnis-Ng et al, 2021; Veron et al, 2019). The study of plant functional traits in insular systems has boosted in recent years, providing important insights into the eco-evolutionary dynamics of these systems (e.g.…”