UC Santa Cruz
Threatened Insular Vertebrates: a Global Assessment of Islands, Threats and Conservation Opportunities
- Author(s): Spatz, Dena R.
- Advisor(s): Croll, Donald
- Tershy, Bernie
- et al.
The loss of biodiversity is one of the most acute global problems. Nowhere in the world are species more at risk of extinction than on islands. Islands represent only 3.2% of the earth’s land area, yet they contain a disproportionately higher amount of threatened and extinct biota compared to continents. The primary cause of extinction has been linked to introduced species, which occur on at least 80% of the world’s archipelagos. The compounding threats of habitat conversion, exploitation, pollution, and coastal hazards linked to climate change make conservation efforts appear complex and intangible. However, the eradication of invasive species from islands is an increasingly utilized conservation tool with a strong record of successes. Removing invasive species from islands has led to substantial conservation benefits and represents a key baseline activity to undertake to restore islands and increase resilience to global change. Consequently, national and local governments and conservation organizations are advancing eradication programs on islands, and there are ongoing developments in eradication technologies. Nonetheless, the global scale of threats to island biodiversity outweighs the resources available for conservation, and data gaps in the distribution of threatened species, and where they co-occurrence with threats, is lacking for most of the world’s islands.
In this dissertation, I fill major data gaps needed to address biodiversity loss on islands and identify islands where invasive species eradications can directly protect threatened species. I examine the distribution of globally threatened species, island characteristics, and threats from invasives, and analyze opportunities for conservation over short and long time frames in the context of invasive species management and global climate changes. Chapter one examines the global distribution of threatened island vertebrates, a well-studied group of taxa that are highly threatened, and whose conservation can subsequently benefit whole island ecosystems, including lesser known taxa. In Chapter 2, I further investigate the biogeography and conservation opportunities on islands for seabirds, one of the most threatened marine groups and one of the few groups that are almost completely reliant on islands to breed. Finally, in Chapter 3, I adapt existing methods in conservation priority setting to score and rank invasive mammal management opportunities on threatened seabird breeding islands, identifying where an eradication can be implemented and achieve the highest conservation benefits. In this chapter, I also examine the potential impact from climate change related coastal hazards and how flooding may impact the long-term success of conservation efforts. Together, these chapters provide insights into the biogeography of the most threatened island vertebrates and can be used to target conservation planning on the islands where biodiversity is in desperate need of conservation.