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Understanding Invasive Species Through Disturbance and Land Use Hypothesis

Invasive species are often ruderals, meaning they thrive in disturbed habitats due to their life history strategy characterized by rapid growth and high reproductive output. The disturbance and land use hypothesis suggests that changes in land use can alter disturbance patterns within ecosystems, creating conditions that favor the establishment and spread of invasive species. These changes can be abrupt or gradual and may lead to altered resource availability, increasing the success of ruderals. Understanding these dynamics is crucial in managing invasive species effectively.

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Understanding Invasive Species Through Disturbance and Land Use Hypothesis

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  1. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Many invasive species have a “ruderal” life history strategy. • “ruderal” = small, very-short lived plants that grow and mature rapidly and that have a large reproductive effort, especially in response to stress

  2. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • These types of species are typically associated with disturbed types of habitats.

  3. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Changes in land use cause changes in the extent and frequency of disturbance to an ecosystem

  4. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt

  5. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual

  6. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual • Change can be permanent

  7. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual • Change can be permanent or transitory

  8. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual • Change can be permanent or transitory • Transition back to original state

  9. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual • Change can be permanent or transitory • Transition to original or new state

  10. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual • Change can be permanent or transitory • Transition to original or new state • Transition can be natural

  11. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Examples from Hobbs in Mooney & Hobbs (2000) • Change can be abrupt or gradual • Change can be permanent or transitory • Transition to original or new state • Transition can be natural or deliberate, with deliberately different end states

  12. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • How can disturbance and land use changes enhance invasions?

  13. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Disturbance and land use changes enhance invasions by: • Changing the amount or flow of resources hence inducing a change in resource availability

  14. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Disturbance and land use changes enhance invasions by: • Changing the amount or flow of resources hence inducing a change in resource availability • Increases the probability of success for ruderals

  15. What makes a species invasive? • i) Disturbance and land use hypothesis • Basic concepts: • Invasive species are ruderals • Ruderals associated with disturbed habitats • Land use changes affect disturbance • Disturbance and land use changes enhance invasions by: • Changing the amount or flow of resources hence inducing a change in resource availability • Increases the probability of success for ruderals • Because of the changes in vegetation states, provides opportunities for other species to exist

  16. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: D’Antonio & Vitousek (1992) • Without invasive species, typically if disturb woodlands, they eventually return back to woodlands Disturbance Recovery

  17. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: D’Antonio & Vitousek (1992) • Without invasive species, eventually return back to woodlands • But if have invasions of alien grasses during or after land is cleared, then alien grasses induce a novel disturbance: fire Disturbance Recovery

  18. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: D’Antonio & Vitousek (1992) • Without invasive species, eventually return back to woodlands • With alien grass invasion: a novel disturbance = fire • Once have a fire, initiate a series of feedback effects that virtually preclude the re-establishment of woody plants Disturbance Recovery

  19. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) • Determined number of alien plants in 12 political regions of Chile • Total of 430 alien weeds • Also 260 alien non-weeds

  20. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) • Number of alien plants in political regions of Chile • For each political region, also determined density of roads and how much land area was in agricultural and urban use • Computed a “Land Use Index” from these that goes from “low” (1) to “intensive” (11)

  21. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) • Number of alien plants in political regions of Chile • Corresponding Land Use Index: from “low” (1) to “intensive” (11) • For alien weeds (A), number increased significantly with index

  22. What makes a species invasive? • i) Disturbance and land use hypothesis • Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) • Number of weedy plants in political regions of Chile • Corresponding Land Use Index: from “low” (1) to “intensive” (11) • Alien weeds increase with intesity of land use • Similarly for Total Number of Alien Species (B)

  23. What makes a species invasive? • i) Disturbance and land use hypothesis • Summary: Disturbance and land use hypothesis • Consistent with ecological theories

  24. What makes a species invasive? • i) Disturbance and land use hypothesis • Summary: Disturbance and land use hypothesis • Consistent with ecological theories • Evidence from a variety of ecosystems

  25. What makes a species invasive? • i) Disturbance and land use hypothesis • Summary: Disturbance and land use hypothesis • Consistent with ecological theories • Evidence from a variety of ecosystems • Empirical correlations

  26. What makes a species invasive? • i) Disturbance and land use hypothesis • Summary: Disturbance and land use hypothesis • Consistent with ecological theories • Evidence from woodland / grasslands • Empirical correlations • But • Is disturbance / land use the factor, or is it something associated with these? • Species traits • Resource availability • Changes in competitive balance • Temporary “vacant” niche

  27. What makes a species invasive? • i) Disturbance and land use hypothesis • Summary: Disturbance and land use hypothesis • Consistent with ecological theories • Evidence from woodland / grasslands • Empirical correlations • But • Is disturbance / land use the factor? • Plant establishment and invasion occur without disturbance

  28. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: • Human activities are the cause of invasive species

  29. Introduced area Geographic Environment Reproduce Home range Disperse Natural area Disturbed area • What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: • Human activities are the cause of invasive species • Humans help invasives overcome barriers; e.g. Richardson et al. (2000) • Humans are the vector for long distance transport

  30. Introduced area Geographic Environment Reproduce Home range Disperse Natural area Disturbed area • What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: • Human activities are the cause of invasive species • Humans help invasives overcome barriers; e.g. Richardson et al. (2000) • Humans overcome geographic barriers • Humans alter the environment that allows plants to grow and reproduce

  31. Introduced area Geographic Environment Reproduce Home range Disperse Natural area Disturbed area • What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: • Human activities are the cause of invasive species • Humans help invasives overcome barriers; e.g. Richardson et al. (2000) • Humans overcome geographic barriers • Humans overcome environmental & reproductive barriers • Humans help disperse invasives in new range

  32. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: • Human activities are the cause of invasive species • Humans help invasives overcome barriers • Thus, humans and invasive species are interdependent

  33. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: FromHobbs in Mooney & Hobbs (2000) • Humans and invasive species are interdependent • Direct effects by introducing invading species

  34. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: FromHobbs in Mooney & Hobbs (2000) • Humans and invasive species are interdependent • Direct effects by introducing invading species • Direct effects by altering ecosystem properties

  35. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: FromHobbs in Mooney & Hobbs (2000) • Humans and invasive species are interdependent • Direct effects by introducing invading species • Direct effects by altering ecosystem properties • Cascading, indirect effects

  36. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: FromHobbs in Mooney & Hobbs (2000) • Humans and invasive species are interdependent • Direct effects by introducing invading species • Direct effects by altering ecosystem properties • Cascading, indirect effects, which sets up an invasive cycle

  37. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction?

  38. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Mack et al. (2000) • Humans as vector for introduction • Lantana camara (lantana; shrub verbena) shrub native to tropical New World • Prized for showy flowers and fragrant leaves

  39. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Mack et al. (2000) • Humans as vector for introduction • Lantana camara native to tropical New World • Introduced as a horticultural species repeatedly throughout the world, especially tropics and sub-tropics

  40. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Lonsdale (1999) Ecology 80:1522-1536 • Humans as vector for introduction • Asked: Do the number of invasive species increase with number of visitors to natural areas?

  41. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Lonsdale (1999) • Humans as vector for introduction • Do invasives ↑ with visitation? • First, control for larger parks have more natives which draws more visitors (a)

  42. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Lonsdale (1999) • Humans as vector for introduction • Do invasives ↑ with visitation? • First, more natives → more visitors • Then look at visitors corrected for number of natives (= “visitor residuals”)

  43. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Lonsdale (1999) • Humans as vector for introduction • Do invasives ↑ with visitation? • First, more natives → more visitors • Then look at visitors corrected for number of natives (= “visitor residuals”) vs. number of exotics (b)

  44. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: From Lonsdale (1999) • Humans as vector for introduction • Do invasives ↑ with visitation? • First, more natives → more visitors • Number of exotics significantly (P<0.001; adj. r2=0.68) with visitors

  45. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction • Human alterations of ecosystem properties

  46. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction • Human alterations of ecosystem properties • Example: Riparian areas in western US • Originally “cottonwood gallery forest” • Cottonwood and willow dominated ecosystem • Open forest with understory of shrubs and herbs • Used by diverse array of animals and birds • Re-establish after spring floods: • Produce abundant wind-dispersed seed in late-spring • Colonize moist, exposed sediments from floods • Grow rapidly (not shade tolerant)

  47. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction • Human alterations of ecosystem properties • Example: Riparian areas in western US • Originally “cottonwood gallery forest” • First large impacts came during Spanish settlement • Primarily ranching and irrigated agriculture

  48. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction • Human alterations of ecosystem properties • Example: Riparian areas in western US • Originally “cottonwood gallery forest” • Spanish settlement: ranching and irrigated agriculture • Expansion of US during mid-1800’s • Trappers removed upstream beavers; resulted in ↑ sediment loads • Large-scale ranching, irrigated agriculture, logging, & mining; resulted in land clearing and extensive disturbance

  49. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction • Human alterations of ecosystem properties • Example: Riparian areas in western US • Originally “cottonwood gallery forest” • Spanish settlement: ranching and irrigated agriculture • US expansion (mid-1800’s): sedimentation, clearing, disturbance • Early 1900’s: Construction of dams, levees, drainage ditches • Prevented spring flood cycle • Dried fuel and litter accumulated → ↑ fires

  50. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction • Human alterations of ecosystem properties • Example: Riparian areas in western US • Originally “cottonwood gallery forest” • Spanish settlement: ranching and irrigated agriculture • US expansion (mid-1800’s): sedimentation, clearing, disturbance • Dam construction (early 1900’s): prevented spring flood; fires • Saltcedars & Russian olive introductions (mid-late 1800’s) • Windbreaks, erosion control & stream bank stabilization, ornamentals • Originally encouraged and subsidized by governments • More drought tolerant; less exacting on seed dispersal & establishment requirements • Now dominant species on much of the riparian areas of western US

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