Reintroducing species when threats still exist: assessing the suitability of contemporary landscapes for island endemics NIC OLE F RANCES ANGEL I and L EE AUSTIN F ITZGERALD


Abstract Reintroducing species into landscapes with per- sistent threats is a conservation challenge. Although historic threats may not be eliminated, they should be understood in the context of contemporary landscapes. Regenerating land- scapes often contain newly emergent habitat, creating op- portunities for reintroductions. The Endangered St Croix ground lizard Pholidoscelis polops was extirpated from the main island of St Croix, U.S. Virgin Islands, as a result of habitat conversion to agriculture and predation by the small Indian mongoose Herpestes auropunctatus. The spe- cies survived on two small cays and was later translocated to two islands. Since the 1950s, new land-cover types have emerged on St Croix, creating a matrix of suitable habitat throughout the island. Here we examined whether the new habitat is sufficient for a successful reintroduction of the St Croix ground lizard, utilizing three complementary approaches. Firstly, we compared a map from 1750 to the current landscape of St Croix and found statistical similarity of land-cover types. Secondly, we determined habitat suit- ability based on a binomial mixture population model de- veloped as part of the programme monitoring the largest extant population of the St Croix ground lizard. We esti- mated the habitat to be sufficient for .142,000 lizards to inhabit St Croix. Thirdly, we prioritized potential reintro- duction sites and planned for reintroductions to take place during 2020–2023. Our case study demonstrates how chan- ging landscapes alter the spatial configuration of threats to species, which can create opportunities for reintroduction. Presuming that areas of degraded habitat may never again be habitable could fail to consider how regenerating land- scapes can support species recovery. When contemporary landscapes are taken into account, opportunities for rein- troducing threatened species can emerge.


Keywords Conservation planning, landscape regeneration, Pholidoscelis polops, reintroduction biology, rewilding, spe- cies repatriation, St Croix ground lizard, Teiidae: Ameiva


NICOLE FRANCES ANGELI* (Corresponding author, orcid.org/0000-0003-3890-


1413)and LEE AUSTIN FITZGERALD ( orcid.org/0000-0001-5648-9480) Biodiversity Research and Teaching Collections, Applied Biodiversity Science Program, Department of Ecology and Conservation Biology, 2258 TAMU, Texas A&M University, College Station, Texas, 77843, USA. E-mail nicoleangeli1@gmail.com


*Current address: Division of Fish and Wildlife, Government of U.S. Virgin Islands, St Croix, USA


Received 1 March 2019. Revision requested 8 May 2019. Accepted 30 August 2019. First published online 2 December 2020.


Supplementary material for this article is available at doi.org/10.1017/S0030605319001091


Introduction


amphibians and birds (Sax & Gaines, 2008). Many endemic species were lost relatively quickly from small islands, and have often persisted only on small offshore islands and in captive colonies (Manne et al., 1999). A conservation goal is to reintroduce species to the islands from which they were extirpated. Even where threats such as invasive preda- tors continue to persist on islands, reintroduction may be possible. The Guidelines to Reintroductions and Other Conservation Translocations (IUCN, 2013,p. 4) state ‘There should generally be strong evidence that the threat(s) that caused any previous extinction have been correctly identified and removed or sufficiently reduced’. Original threats need to be addressed, but they should be understood in the present context. Often original threats such as the presence of mongooses on large islands cannot be com- pletely eliminated with current technologies. The Guideline’s phrasing ‘sufficiently reduced’ implies that large-scale res- toration efforts are a prerequisite for reintroductions. How- ever, an alternative way of addressing persistent threats is to understand them in the context of contemporary land- scapes that have emerged since losses originally occurred. Extinction/extirpation takes place in a landscape context, and changes of those landscapes over time result in altered threats to biodiversity. Restoration efforts in newly develop- ing ecosystems will thus benefit from fresh approaches and newnorms (Hobbs et al., 2009). There may be opportunities for reintroductions into emergent habitats and natural refu- gia that were not present during historic extirpation events. This can apply to islands where landscapes are regenerating, even when some historic drivers of extinction such as inva- sive predators are still present. Human land use changes the configuration of landscape


T


features, influencing species’ distributions. Changing polit- ical and economic factors also alter prospects for landscape restoration (Wintle et al., 2011). In eastern North America, reduction in agricultural activities allowed regeneration of forests that sustain populations of numerous species, in- cluding the red wolf Canis rufus and red-legged salamander


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Oryx, 2021, 55(3), 344–351 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319001091


he majority of island endemics lost to invasive exotic mammals over the past 500 years have been reptiles,


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