Absence of evidence is not evidence of absence: Knowledge shortfalls threaten the effective conservation of freshwater crocodiles

Ruchira Somaweera, Mathew L. Brien, Tracy Sonneman, Raphael K. Didham, Bruce L. Webber

Research output: Contribution to journalReview article

Abstract

The extensive alteration of freshwater habitat across the globe has resulted in the decline of a number of wildlife species, some of which now face extinction. Large-bodied species are frequently at greatest risk. However, identifying the direct and indirect pathways of impact on these long-lived and often cryptic predators has proven challenging. Since the cessation of commercial crocodile hunting in northern Australia in the 1970s, the assumption has been that populations of both the saltwater crocodile (Crocodylus porosus) and freshwater crocodile (Crocodylus johnstoni) would recover naturally. While extensive population monitoring of the saltwater crocodile has occurred, there has been limited ongoing monitoring of the freshwater crocodile to test this assumption. Moreover, there is growing concern that the increasing threat from global environmental change, including invasive alien species, anthropogenic landscape modification, agricultural pollutants, and other human activities, may jeopardise the recovery and long-term conservation of the freshwater crocodile. Here we summarise existing knowledge on the various direct and indirect threats this species faces and prioritise future actions to increase the likelihood of effective conservation outcomes for freshwater crocodiles. Although an in-depth understanding of the magnitude and dynamics of the majority of these emerging threats is still lacking, it is becoming clear that they are acting in previously unexpected ways, leading to novel combinations of cascading direct and indirect impacts.

Original languageEnglish
Article numbere00773
JournalGlobal Ecology and Conservation
Volume20
DOIs
Publication statusPublished - 1 Oct 2019

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crocodiles
Crocodylus porosus
Crocodylus
monitoring
global change
invasive species
anthropogenic activities
wildlife
extinction
pollutants
crocodile
introduced species
hunting
predators
environmental change
human activity
habitats
predator
pollutant
habitat

Cite this

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title = "Absence of evidence is not evidence of absence: Knowledge shortfalls threaten the effective conservation of freshwater crocodiles",
abstract = "The extensive alteration of freshwater habitat across the globe has resulted in the decline of a number of wildlife species, some of which now face extinction. Large-bodied species are frequently at greatest risk. However, identifying the direct and indirect pathways of impact on these long-lived and often cryptic predators has proven challenging. Since the cessation of commercial crocodile hunting in northern Australia in the 1970s, the assumption has been that populations of both the saltwater crocodile (Crocodylus porosus) and freshwater crocodile (Crocodylus johnstoni) would recover naturally. While extensive population monitoring of the saltwater crocodile has occurred, there has been limited ongoing monitoring of the freshwater crocodile to test this assumption. Moreover, there is growing concern that the increasing threat from global environmental change, including invasive alien species, anthropogenic landscape modification, agricultural pollutants, and other human activities, may jeopardise the recovery and long-term conservation of the freshwater crocodile. Here we summarise existing knowledge on the various direct and indirect threats this species faces and prioritise future actions to increase the likelihood of effective conservation outcomes for freshwater crocodiles. Although an in-depth understanding of the magnitude and dynamics of the majority of these emerging threats is still lacking, it is becoming clear that they are acting in previously unexpected ways, leading to novel combinations of cascading direct and indirect impacts.",
keywords = "Agricultural pollutants, Crocodylus johnstoni, global change, Indirect impacts, Invasive alien species, Species interactions, Trophic cascades",
author = "Ruchira Somaweera and Brien, {Mathew L.} and Tracy Sonneman and Didham, {Raphael K.} and Webber, {Bruce L.}",
year = "2019",
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language = "English",
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T1 - Absence of evidence is not evidence of absence

T2 - Knowledge shortfalls threaten the effective conservation of freshwater crocodiles

AU - Somaweera, Ruchira

AU - Brien, Mathew L.

AU - Sonneman, Tracy

AU - Didham, Raphael K.

AU - Webber, Bruce L.

PY - 2019/10/1

Y1 - 2019/10/1

N2 - The extensive alteration of freshwater habitat across the globe has resulted in the decline of a number of wildlife species, some of which now face extinction. Large-bodied species are frequently at greatest risk. However, identifying the direct and indirect pathways of impact on these long-lived and often cryptic predators has proven challenging. Since the cessation of commercial crocodile hunting in northern Australia in the 1970s, the assumption has been that populations of both the saltwater crocodile (Crocodylus porosus) and freshwater crocodile (Crocodylus johnstoni) would recover naturally. While extensive population monitoring of the saltwater crocodile has occurred, there has been limited ongoing monitoring of the freshwater crocodile to test this assumption. Moreover, there is growing concern that the increasing threat from global environmental change, including invasive alien species, anthropogenic landscape modification, agricultural pollutants, and other human activities, may jeopardise the recovery and long-term conservation of the freshwater crocodile. Here we summarise existing knowledge on the various direct and indirect threats this species faces and prioritise future actions to increase the likelihood of effective conservation outcomes for freshwater crocodiles. Although an in-depth understanding of the magnitude and dynamics of the majority of these emerging threats is still lacking, it is becoming clear that they are acting in previously unexpected ways, leading to novel combinations of cascading direct and indirect impacts.

AB - The extensive alteration of freshwater habitat across the globe has resulted in the decline of a number of wildlife species, some of which now face extinction. Large-bodied species are frequently at greatest risk. However, identifying the direct and indirect pathways of impact on these long-lived and often cryptic predators has proven challenging. Since the cessation of commercial crocodile hunting in northern Australia in the 1970s, the assumption has been that populations of both the saltwater crocodile (Crocodylus porosus) and freshwater crocodile (Crocodylus johnstoni) would recover naturally. While extensive population monitoring of the saltwater crocodile has occurred, there has been limited ongoing monitoring of the freshwater crocodile to test this assumption. Moreover, there is growing concern that the increasing threat from global environmental change, including invasive alien species, anthropogenic landscape modification, agricultural pollutants, and other human activities, may jeopardise the recovery and long-term conservation of the freshwater crocodile. Here we summarise existing knowledge on the various direct and indirect threats this species faces and prioritise future actions to increase the likelihood of effective conservation outcomes for freshwater crocodiles. Although an in-depth understanding of the magnitude and dynamics of the majority of these emerging threats is still lacking, it is becoming clear that they are acting in previously unexpected ways, leading to novel combinations of cascading direct and indirect impacts.

KW - Agricultural pollutants

KW - Crocodylus johnstoni

KW - global change

KW - Indirect impacts

KW - Invasive alien species

KW - Species interactions

KW - Trophic cascades

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U2 - 10.1016/j.gecco.2019.e00773

DO - 10.1016/j.gecco.2019.e00773

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