Invasive plants and native plant extinctions :

1. Invasive plants and native plant extinctions: a framework for management Paul Downey

3. wide acknowledgement that invasive plants are a global threat to biodiversity New Zealand Journal of Ecology12: 1-16 (1997) BioScience 48: 607-615 (1998) PLoS Biology12 e1001850 (2014) Proceedings of the Royal Society London B 270: 775-781 (2003).

4. many examples of extinctions of native vertebrates due to invasive vertebrates 2011

5. many examples of extinctions of native vertebrates due to invasive vertebrates 2011 especially on islands

6. Lygodiummicrophyllum Florida Mimosa pigra northern Australia Noexamples of extinctions of native plants due to invasive plants Heracleum mantegazzianumCzech Republic Andropogongayanus northern Australia

7. extinction debate

8. the impact of invasive plants has been questioned Trends in Ecology and Evolution19: 470-474 (2004) Journal of Agricultural and Environmental Ethics18: 215-236 (2005) PNAS105: 11490-11497 (2008) PNAS 112: 4387–4392 (2015).

9. the impact of invasive plants has been questioned Trends in Ecology and Evolution19: 470-474 (2004) “The negative effects have been exaggerated in many parts of the world.” Journal of Agricultural and Environmental Ethics18: 215-236 (2005) PNAS105: 11490-11497 (2008) PNAS 112: 4387–4392 (2015).

10. How should we interpret the fact that there is no clear evidence of extinctions?

11. How should we interpret the fact that there is no clear evidence of extinctions? What do we know?

12. Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally a

13. Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally a b plant extinction is

14. Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally a b c Many studies on impacts use measures that are unlikely to demonstrate extinctions (e.g. species richness) plant extinction is

15. Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally a b c d Many studies on impacts use measures that are unlikely to demonstrate extinctions (e.g. species richness) plant extinction is Number of extinct species is NOT the appropriate metric to quantify the impacts on native plant species!!

16. Abundant evidence that plant invasions have had MAJOR impacts on native plant species from many regions, globally a b c d e Many studies on impacts use measures that are unlikely to demonstrate extinctions (e.g. species richness) plant extinction is 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.

17. prerequisites for demonstrating extinction from alien plant invasion

18. Four prerequisites 1 the processes by which an alien plant poses a threat

19. Four prerequisites 1 2 the processes by which an alien plant poses a threat the level to which the threat action is applied relative to the tolerance of the native species to the threat

20. Four prerequisites 1 2 3 the processes by which an alien plant poses a threat the level to which the threat action is applied relative to the tolerance of the native species to the threat the timeframe over which the threat is active relative to the life history of native plants

21. Four prerequisites 1 2 3 4 the processes by which an alien plant poses a threat the level to which the threat action is applied relative to the tolerance of the native species to the threat the timeframe over which the threat is active relative to the life history of native plants the spatial relationship between the threat applied in 1-3 relative to the distribution of the native plant species

22. refocusing the debate

23. Extinction trajectory The threat posed by invasive alien plants is best conceptualized as a continuum or trajectoryfrom no impact through to extinction with a series of thresholds. No impact to native species (population stable or increasing) degree of threat

24. Extinction trajectory Extinction is not the only threshold on the trajectory! Loss of individuals leading to a declining population Population stable or increasing extinction timeline 1 Threshold Loss of individuals leading to a declining population

25. Extinction trajectory Extinction is not the only threshold on the trajectory! Loss of individuals leading to a declining population Loss of some populations which maintain a seed bank Population stable or increasing extinction timeline 1 2 Threshold Loss of some populations which maintain a seed bank

26. Extinction trajectory Extinction is not the only threshold on the trajectory! Loss of individuals leading to a declining population Loss of some populations which maintain a seed bank Loss of populations including seed banks Population stable or increasing extinction timeline 3 1 2 Threshold Loss of populations including seed banks

27. Extinction trajectory Extinction is not the only threshold on the trajectory! Decaying persistent seed bank – no living individuals present in any population Loss of individuals leading to a declining population Loss of some populations which maintain a seed bank Loss of populations including seed banks Population stable or increasing extinction timeline 3 1 4 2 Threshold Decaying persistent seed bank – no living individuals present in any population

28. Extinction trajectory Extinction is not the only threshold on the trajectory! Decaying persistent seed bank – no living individuals present in any population Loss of individuals leading to a declining population Loss of some populations which maintain a seed bank Loss of populations including seed banks Propagules and individuals occur ex-situ Population stable or increasing extinction timeline 3 1 4 5 2 Threshold Propagules and individuals occur ex-situ

29. Extinction trajectory Decaying persistent seed bank – no living individuals present in any population Loss of individuals leading to a declining population Loss of some populations which maintain a seed bank Loss of populations including seed banks Propagules and individuals occur ex-situ Species extinct Population stable or increasing extinction timeline 3 6 1 4 5 2 Threshold Species extinct

30. population stable or increasing decline model 1 2 I = gradual linear II = rapid III = threshold III I Population size II threshold number Seed bank only present Level of threat relative to time

31. population stable or increasing threshold number Example of a species that has a rapid population decline, but a persistent seed bank 1 2 3 population size II Species status III II = rapid III = threshold seed bank or propagule availability size threshold number Level of threat relative to time

33. threshold number Extinction trajectory population stable or increasing population size 3 2 1 Demonstrating categorically that thresholds 4, 5 and 6 have been breached may be difficult seed bank or propagule availability size III III III III III number of populations species status I I I I I II II II II II 4 seed bank or propagule availability size 5 ex-situ population size 6 species extinct level of threat relative to time

34. Extinction trajectory threshold number population stable or increasing 1 Data to demonstrate that thresholds 1 and 2 (and to a lesser extent 3) have been crossed exists for many species. population size 2 seed bank or propagule availability size 3 III III III III III number of populations species status I I I I I II II II II II 4 seed bank or propagule availability size 5 ex-situ population size 6 species extinct level of threat relative to time

35. management of alien plants Active management of alien plants is likely to have off-set some extinctions and/or reversed thresholds

36. questionable assumption invasive plant control will lead to positive conservation outcomes

37. ACT Woodlands and the threat of extinction from plant invasions

38. Invasive plants managed in ACT woodlands African lovegrass blackberry Chilean needle grass serrated tussock St. John’s wort Cootamundra wattle great mullein other woody weeds Paterson’s curse saffron thistle sweet briar Hectares Source: collector app 35 specific species listed (plus unspecified control)

39. Invasive plants managed in ACT woodlands

40. Invasive plants managed in ACT woodlands

41. Invasive plants managed in ACT woodlands

42. Invasive plants managed in ACT woodlands

43. ACT Woodlands and the threat of extinction from alien plant invasions need to align management to thresholds

44. What’s threatened? and Which extinction threshold has been breached?

45. Invasive plants managed in ACT woodlands change the structure = threshold 1

46. Invasive plants managed in ACT woodlands

47. Invasive plants managed in ACT woodlands

48. Invasive plants managed in ACT woodlands in NSW 15 of these invasive plants threaten 78 native plants

49. Future for ACT Woodlands Improve linkages between conservation and invasive plant management

50. Future for ACT Woodlands Improve linkages between conservation and invasive plant management Outcomes for biodiversity