Invasive plants and native plant extinctions Paul Downey a framework for management BioScience 48 607615 1998 New Zealand Journal of Ecology 12 116 1997 PLoS Biology 12 e1001850 2014 ID: 767183
Download Presentation The PPT/PDF document "Invasive plants and" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Invasive plants and native plant extinctions : Paul Downey a framework for management
BioScience 48: 607-615 (1998) New Zealand Journal of Ecology 12: 1-16 (1997) PLoS Biology 12 e1001850 (2014) Proceedings of the Royal Society London B 270: 775-781 (2003).wide acknowledgement that invasive plants are a global threat to biodiversity
many examples of extinctions of native vertebrates due to invasive vertebrates 2011
many examples of extinctions of native vertebrates due to invasive vertebrates 2011 especially on islands
No examples of extinctions of native plants due to invasive plants Mimosa pigra northern Australia Lygodium microphyllum Florida Heracleum mantegazzianum Czech Republic Andropogon gayanus northern Australia
extinction debate
Journal of Agricultural and Environmental Ethics 18: 215-236 (2005) Trends in Ecology and Evolution 19: 470-474 (2004) the impact of invasive plants has been questioned PNAS 112: 4387–4392 (2015).PNAS 105: 11490-11497 (2008)
Journal of Agricultural and Environmental Ethics 18: 215-236 (2005) Trends in Ecology and Evolution 19: 470-474 (2004) the impact of invasive plants has been questioned PNAS 112: 4387–4392 (2015).PNAS 105: 11490-11497 (2008)“The negative effects have been exaggerated in many parts of the world.”
How should we interpret the fact that there is no clear evidence of extinctions?
How should we interpret the fact that there is no clear evidence of extinctions? What do we know?
Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally a
plant extinction is Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally ab
plant extinction is Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally aMany studies on impacts use measures that are unlikely to demonstrate extinctions (e.g. species richness)b c
plant extinction is Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally aMany studies on impacts use measures that are unlikely to demonstrate extinctions (e.g. species richness)Number of extinct species is NOT the appropriate metric to quantify the impacts on native plant species!! bc d
plant extinction is Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally aMany studies on impacts use measures that are unlikely to demonstrate extinctions (e.g. species richness)Number of extinct species is NOT the appropriate metric to quantify the impacts on native plant species!! Seed banks complicate things: a) extremely long-lived (max. >400 yrs) b) hard to sample Thus very difficult to state conclusively that no propagules exist. b c d e
prerequisites for demonstrating extinction from alien plant invasion
the processes by which an alien plant poses a threat Four prerequisites 1
the processes by which an alien plant poses a threat Four prerequisites 1 the level to which the threat action is applied relative to the tolerance of the native species to the threat2
the processes by which an alien plant poses a threat Four prerequisites 1 the level to which the threat action is applied relative to the tolerance of the native species to the threat2the timeframe over which the threat is active relative to the life history of native plants3
the processes by which an alien plant poses a threat Four prerequisites 1 the level to which the threat action is applied relative to the tolerance of the native species to the threat2the timeframe over which the threat is active relative to the life history of native plants3 the spatial relationship between the threat applied in 1-3 relative to the distribution of the native plant species4
refocusing the debate
E xtinction trajectory The threat posed by invasive alien plants is best conceptualized as a continuum or trajectory from no impact through to extinctionwith a series of thresholds. degree of threatNo impact to native species (population stable or increasing)
extinction timeline L oss of individuals leading to a declining population 1 P opulation stable or increasing ThresholdExtinction trajectoryLoss of individuals leading to a declining population Extinction is not the only threshold on the trajectory!
extinction timeline 2 L oss of individuals leading to a declining population L oss of some populations which maintain a seed bank 1Population stable or increasingThreshold E xtinction trajectory L oss of some populations which maintain a seed bank E xtinction is not the only threshold on the trajectory!
extinction timeline 2 3 1 Threshold L oss of populations including seed banksLoss of populations including seed banks Extinction is not the only threshold on the trajectory! E xtinction trajectory L oss of individuals leading to a declining population L oss of some populations which maintain a seed bank P opulation stable or increasing
extinction timeline D ecaying persistent seed bank – no living individuals present in any population 2 34 1 Threshold D ecaying persistent seed bank – no living individuals present in any population E xtinction is not the only threshold on the trajectory! E xtinction trajectory L oss of populations including seed banks L oss of individuals leading to a declining population L oss of some populations which maintain a seed bank P opulation stable or increasing
extinction timeline P ropagules and individuals occur ex-situ 2 34 5 1 Threshold P ropagules and individuals occur ex-situ E xtinction is not the only threshold on the trajectory! E xtinction trajectory D ecaying persistent seed bank – no living individuals present in any population L oss of populations including seed banks L oss of individuals leading to a declining population L oss of some populations which maintain a seed bank P opulation stable or increasing
extinction timeline D ecaying persistent seed bank – no living individuals present in any population P ropagules and individuals occur ex-situ2Loss of individuals leading to a declining populationLoss of some populations which maintain a seed bank 3 4 5 6 1 P opulation stable or increasing Threshold L oss of populations including seed banks S pecies extinct S pecies extinct E xtinction trajectory
L evel of threat relative to time Population size population stable or increasing S eed bank only present I II III 1 2 threshold number decline model I = gradual linear II = rapid III = threshold
L evel of threat relative to time population size population stable or increasing threshold number II = rapid III = threshold seed bank or propagule availability size III II 2 threshold number 1 3 S pecies status E xample of a species that has a rapid population decline, but a persistent seed bank
Demonstrating categorically thatthresholds 4, 5 and 6 have been breached may be difficult E xtinction trajectory level of threat relative to time population size population stable or increasing species extinct I II III I II III I II III I II III I II III seed bank or propagule availability size number of populations seed bank or propagule availability size ex-situ population size 1 2 3 4 5 6 species status threshold number
Data to demonstrate that thresholds 1 and 2 (and to a lesser extent 3) have been crossed exists for many species. Extinction trajectory level of threat relative to time population size population stable or increasing species extinct I II III I II III I II III I II III I II III seed bank or propagule availability size number of populations seed bank or propagule availability size ex-situ population size 1 2 3 4 5 6 species status threshold number
management of alien plants A ctive management of alien plants is likely to have off-set some extinctions and/or reversed thresholds
questionable assumption invasive plant control will lead to positive conservation outcomes
ACT Woodlands and the threat of extinction from plant invasions
African lovegrass blackberry Chilean needle grass serrated tussockSt. John’s wortCootamundra wattle great mulleinother woody weedsPaterson’s cursesaffron thistlesweet briar HectaresSource: collector appInvasive plants managed in ACT woodlands 35 specific species listed (plus unspecified control)
Invasive plants managed in ACT woodlands
Invasive plants managed in ACT woodlands
Invasive plants managed in ACT woodlands
Invasive plants managed in ACT woodlands
ACT Woodlands and the threat of extinction from alien plant invasions need to align management to thresholds
What’s threatened ? and Which extinction threshold has been breached?
change the structure = threshold 1 Invasive plants managed in ACT woodlands
Invasive plants managed in ACT woodlands
Invasive plants managed in ACT woodlands
Invasive plants managed in ACT woodlands in NSW 15 of these invasive plants threaten 78 native plants
Future for ACT Woodlands Improve linkages between conservation and invasive plant management
Future for ACT Woodlands Improve linkages between conservation and invasive plant management Outcomes for biodiversity
extinction too late for management thanks and questions Downey, P.O. and Richardson, D.M. (2016). Alien plant invasions and native plant extinctions : a six-threshold framework. AoB Plants 8, plw047.