Water Availability Coincides with Population Declines for an Endangered Butterfly

Heather Cayton,Nick Haddad

doi:10.3390/d10030094

Abstract

As global climate change causes population declines across numerous taxa, it becomes critical to understand the specific pathway by which climatic and anthropogenic factors influence population size. Water availability is a key environmental condition that links climate and humans to species response, especially for rare or threatened butterflies that are highly sensitive to changes in climate and the surrounding landscape. We use the wetland-dependent endangered St. Francis’ satyr butterfly (Neonympha mitchellii francisci) to test how changes in water availability affect population size via changes in host plant growth. We show that long-term declines in water availability are directly linked to a decline in host plant growth and contributed to a population decrease of 95% for St. Francis’ satyrs in the past decade, threatening the persistence of the species. Recent restoration work, which includes efforts to increase water availability via hardwood removal, has been successful in increasing population numbers. Many butterflies are broadly dependent on water availability and flow, and only by understanding the specific pathway that directly links water availability to species response can we make effective conservation plans to prepare for the altered water conditions of the future.

Highlights

Global climate change has contributed to population declines across numerous taxa [1,2,3,4].These declines are exacerbated by human modification of the landscape [5], when that modification alters or removes critical natural resources from the environment and limits options for adaptation [6]
We present for a rare butterfly species
Bragg region has significantly present for a rare butterfly species

Summary

Introduction

Global climate change has contributed to population declines across numerous taxa [1,2,3,4].These declines are exacerbated by human modification of the landscape [5], when that modification alters or removes critical natural resources from the environment and limits options for adaptation [6]. Some mechanisms by which climate and humans interact to influence ecosystem processes and species interactions have been identified [7,8], the pathway that leads to quantifiable declines in population numbers remains unclear [3,9] This is especially true for changes to precipitation and water availability that can have the most extreme effects on populations of rare species, as we show here. Changes in precipitation patterns directly impact both water availability and flow, which would have a large impact on wetland and riparian species, but on many species generally sensitive to topography and microclimate around water sources [12,13] These effects could be exacerbated by increases in the local human population and land use, for example via increased water consumption or greater fragmentation of riparian ecosystems [14,15]

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Conclusion