Ecosystem services the significance of contributions by invasive plant species

Transcription

1 Ecosystem services the significance of contributions by invasive plant species Steve Young, University of Nebraska -Lincoln; Jeff Corbin, Union College, New York; Valerie Eviner, University of California -Davis; Chris Dionigi, National Invasive Species Council; Craig Allen, University of Nebraska -Lincoln; Colin Brooks, M ichigan Tech Research Institute; Lori Williams, National Invasive Species Council

2 Outline Discuss invasive plant species (IPS) impacts Define ecosystem services Present information on: A theoretical framework for assessing invasive plant species and ecosystem services The practical considerations for reducing invasive plant species impacts on ecosystem services Summary

3 Outline Discuss invasive plant species (IPS) impacts Define ecosystem services Present information on: A theoretical framework for assessing invasive plant species and ecosystem services The practical considerations for reducing invasive plant species impacts on ecosystem services Summary

4 Bromus tectorum Spartina alterniflora Tamarix spp. Myrica faya Genista monspessulana

5 Invasive plant species Present in nearly every region and most habitat types Fraction of flora that is exotic for 184 sites around the world, broken down by: Region Biome Source: Lonsdale 1999

6 Invasive plant species Present in nearly every region and most habitat types Economic impact > $120 billion per year in US (Pimental et al. 2005)

7 Invasive plant species Present in nearly every region and most habitat types Economic impact > $120 billion per year in US (Pimental et al. 2005) Invasion frequencies are increasing

8 Outline Discuss invasive plant species (IPS) impacts Define ecosystem services Present information on: A theoretical framework for assessing invasive plant species and ecosystem services The practical considerations for reducing invasive plant species impacts on ecosystem services Summary

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12 Ecosystem services Millennium ecosystem assessment (2005)

13 Ecosystem services Millennium ecosystem assessment (2005) Provisioning Food, fresh water, pharmas, energy, fiber

14 Ecosystem services Millennium ecosystem assessment (2005) Provisioning Food, fresh water, pharmas, energy, fiber Regulation C sequestration, flood control, pest control

15 Ecosystem services Millennium ecosystem assessment (2005) Provisioning Food, fresh water, pharmas, energy, fiber Regulation C sequestration, flood control, pest control Cultural Aesthetics, heritage, recreation, spiritual

16 Ecosystem services Millennium ecosystem assessment (2005) Supporting Nutrient cycling, Seed dispersal, Primary Productivity Provisioning Food, fresh water, pharmas, energy, fiber Regulation C sequestration, flood control, pest control Cultural Aesthetics, heritage, recreation, spiritual

17 Biodiversity Ecosystem services Millennium ecosystem assessment (2005) Supporting Nutrient cycling, Seed dispersal, Primary Productivity Provisioning Food, fresh water, pharmas, energy, fiber Regulation C sequestration, flood control, pest control Cultural Aesthetics, heritage, recreation, spiritual

18 Biodiversity Ecosystem services Millennium ecosystem assessment (2005) Supporting Nutrient cycling, Seed dispersal, Primary Productivity Provisioning Food, fresh water, pharmas, energy, fiber Regulation C sequestration, flood control, pest control Cultural Aesthetics, heritage, recreation, spiritual MANY categories declining under current scenarios

19 Outline Discuss invasive plant species (IPS) impacts Define ecosystem services Present information on: A theoretical framework for assessing invasive plant species and ecosystem services The practical considerations for reducing invasive plant species impacts on ecosystem services Summary

20 How do we assess ecosystem services? Indicators must be: Representative Reliable Feasible Current assessments: because ecosystem services can be difficult to measure directly, scientists have tended to use land use land cover as a proxy for the provision of services even though the relationships between land use land cover and service provision are largely untested for most services in most regions of the world. (Bennett et al. 2009)

21 What do we need to understand to manage ecosystem services? Who are the key ecosystem service providers? What are the components of community structure that influence function at landscape level? (e.g. compensatory mechanisms) What are the key environmental factors? What are the spatio-temporal scales over which providers and services operate? Kremen 2005

22 % precip available Mark and Dickinson 2008

23 Water quantity Forage production Carbon storage Flood control High precip- ET climate, NPP, Plant biomass land use, forage quality, (AG+ BG) veg. type grazing tolerance distribution sales livestock products Low Chan et al. 2006

24 Ecosystem processes that impact water supply Braumann et al 2007

25 Effects of removal of native trees - estimates vary by scale Wilcox et al. 2006

26 How are ecosystem services different from functions? Services often integrate across multiple ecosystem functions and attributes Emphasis on scale & location Emphasis on multiple services and tradeoffs Distribution of services depends on distribution of functions as well as human demands

27 Assessment and prediction of ecosystem services impacted by IPS Can we use ecosystem functions as proxies for services? How strong are our broad generalizations about the ecosystem impacts of invaders? How do we move beyond these generalizations to consider: Context- dependence: environment Abundance Community interactions Temporal scale Spatial scale Heterogeneity within vegetation types Heterogeneity across landscape Scale at which services are regulated Scale at which ecosystem functions are needed for human use How do we integrate all of these factors?

28 Assessment and prediction of ecosystem services impacted by IPS Can we use ecosystem functions as proxies for services? We already have a strong understanding of many species effects on ecosystem functions. Ecosystem functions can be used as proxies for services, but care must be taken to consider how services integrate these component functions over space and time Even with these caveats, predictions based on functions are likely to be an improvement over current assessment techniques (particularly when we incorporate the mechanisms to be discussed later)

29 How do invaders impact services? Charles & Dukes 2007

30 Assessment and prediction of ecosystem services impacted by IPS Can we use ecosystem functions as proxies for services? How strong are our broad generalizations about the ecosystem impacts of invaders? How do we move beyond these generalizations to consider: Context- dependence: environment Abundance Community interactions Temporal scale Spatial scale Heterogeneity within vegetation types Heterogeneity across landscape Scale at which services are regulated Scale at which ecosystem functions are needed for human use How do we integrate all of these factors?

31 Moving from all invaders to functional-type generalizations Invaders that provide novel functional types have large impacts N fixers (increase decomposition, nitrogen cycling) Woody invasion into grasslands (tend to decrease water provision, increase carbon sequestration) High biomass producers near waterways (WUE and spread rate compared to native vegetation)

32 Soil C impacts of woody invasion into grasslands Increase C Decrease C Jackson et al 2002

33 What about less obvious changes? (when invasions are similar vegetation structure)

34 What about less obvious changes? (water use by vegetation ) Johns 1989

35 Russian olive Seasonal ET (May 1 Through September 1, 2005) 26.7 Inches OR 2.23 Acre-feet Water, AVERAGE Equals 23.8 Gallons Water Per Plant Per Day* Seasonal LOW Of 11.8 Inches Water 10.5 Gallons Water Per Plant Per Day* Seasonal HIGH Of 41.5 Inches Water 36.9 Gallons Water Per Plant Per Day* OR OR Hergert et al., 2010

36 Saltcedar Seasonal ET (May 1 Through September 1, 2005) 26.8 Inches OR 2.23 Acre-feet Water, AVERAGE Equals 21.6 Gallons Water Per Plant Per Day* Seasonal LOW Of 13.8 Inches Water 11.1 Gallons Water Per Plant Per Day* Seasonal HIGH Of 37.8 Inches Water 30.5 Gallons Water Per Plant Per Day* OR OR Hergert et al., 2010

37 Assessment and prediction of ecosystem services impacted by IPS How strong are our broad generalizations about the ecosystem impacts of invaders? Our broad generalizations of the impacts of vegetation types on ecosystem functions are a good first step Management and updated theory should be based on measurements of individual invaders across space and time collectively, these measurements can build a better predictive framework Need a better ability to predict impacts within broad groups of plants- multiple traits are strong predictors

38 Assessment and prediction of ecosystem services impacted by IPS Can we use ecosystem functions as proxies for services? How strong are our broad generalizations about the ecosystem impacts of invaders? How do we move beyond these generalizations to consider: Context- dependence: environment Abundance Community interactions Temporal scale Spatial scale Heterogeneity within vegetation types Heterogeneity across landscape Scale at which services are regulated Scale at which ecosystem functions are needed for human use How do we integrate all of these factors?

39 Assessment and prediction of ecosystem services impacted by IPS How do we move beyond these generalizations to consider: Context- dependence: environment Different traits regulate functions in different environments A given species alters its traits in response to its environment Abundance/community interactions Ecosystem effects vary with abundance (linear vs. non-linear?) Impact of abundance depends on similarity in function

40 What density does a plant need to be at to have an ecosystem effect? Fyles & Fyles % fir 100% alder 100% fir 100% alder

41 Non-natives impact soils even at less than 3% of community biomass Invaders present Soil C (%) Microbial activity (μg CO 2 -C g 1 soil h 1 ) Invaders removed Natives + invaders Natives only Invaders only Peltzer et al. 2009

42 Assessment and prediction of ecosystem services impacted by IPS How do we move beyond these generalizations to consider: Context- dependence: environment Different traits regulate functions in different environments A given species alters its traits in response to its environment Abundance/community interactions Ecosystem effects vary with abundance (linear vs. non-linear?) Impact of abundance depends on similarity in function Spatiotemporal scale Heterogeneity within vegetation types and across landscapes Scales at which services and functions are regulated and needed for human use, respectively

43 Spatiotemporal scales Variability Annual (e.g. cheatgrass NPP varies 10-fold year to year) Seasonal Hot moments Thresholds Directional shifts over time MEA 2005

44 Different patches of landscape provide different services Invasions may alter services by making landscape more homogenous Location of invasion on landscape matters MEA 2005

45 Assessment and prediction of ecosystem services impacted by IPS Requires integration across complexity : The effects of invaders on ecosystem functions changes with environment, abundance, community interactions, space and time. Current trait-based predictive frameworks can be expanded, and coupled with landscape theory to predict these variations

46 Outline Discuss invasive plant species (IPS) impacts Define ecosystem services Present information on: A theoretical framework for assessing invasive plant species and ecosystem services The practical considerations for reducing invasive plant species impacts on ecosystem services Summary

47 The practicality of invasive plant species and ecosystem services How have invasive species affected ecosystem services? Can we restore ecosystem services following invasion?

48 The practicality of invasive plant species and ecosystem services Not all exotic species are equal need to prioritize Species impacts driven by species traits and habitat characteristics, among other factors Removal is often not enough - legacies

49 Invasive species and biodiversity Wilcove et al. (1998) Causes of decline for threatened/endangered species in U.S. All species (n=1880) Plants (n=1055) Habitat degradation/loss 85% 81% Alien species 49% 57% Pollution 24% 7% Overexploitation 17% 10% Disease 3% 1%

50 Significant community changes California grasslands Semi-arid shrublands Freshwater wetlands Forest understories

51 Biodiversity Wilcove et al. (1998) - >49% of listed species in U.S. affected by invasive species Gurevich and Padilla (2004) Multiple factors: land-use, invasive species, among others, can t be separated Sax and Gaines (2008) Species invasions may increase biodiversity The role of invasive species in extinctions of plants may be overstated, but significant shifts are occurring in community composition

52 Supporting services Provide indirect benefits to humans, through other services Invasive species often (not always) increase net primary productivity and net N cycling rates Invasive plant species have increased some measures, but this is not necessarily beneficial

53 Provisioning services Water hyacinth in Lake Victoria, Kenya Agricultural run-off and nutrient-rich sediment 1998: >20,000 ha 2005 Nearly absent 2006 Reinvasion following heavy rains and nutrient influx Source: NASA

54 Provisioning services Water hyacinth in Lake Victoria, Kenya Agricultural run-off and nutrient-rich sediment 1998: >20,000 ha 2005 Nearly absent 2006 Reinvasion following heavy rains and nutrient influx Consequences: Dead zones and loss of fishing productivity Source: NASA

55 Provisioning services Food, fresh water, pharmaceutical products, energy, fiber Agricultural pests weeds, pathogens, diseases Weeds decrease agricultural productivity by ~12% Degrade pasture land e.g. leafy spurge, St. John s wort Well-established negative impacts of invasive plant species on provisioning services

56 Regulating services C sequestration Meta-analysis of effects of invasion on ecosystem C pools (Liao et al. 2008) Carbon pool % increase in pool size (native exotic) Shoots 133 ± 2 84 Roots 5 ± 3 60 Litter 49 ± 9 16 Soil 6 ± 1 83 Soil microbes 34 ± 6 14 n

57 Regulating services C sequestration Flood control - Tamarix spp. in southwest

58 Tamarix spp. Shrub or small tree introduced from Eurasia Invades riparian habitat Widespread in arid and semi-arid North America

59 Tamarix spp. - Impacts Displaces native vegetation Increases fire frequency Increases water transpiration depleting groundwater - Consumes m 3 ha -1 yr -1 more water than native veg - (Annual precipitation < 4500 m 3 ha -1 yr -1 ) Increases flooding, erosion rates

60 Regulating services C sequestration Flood control - Tamarix spp. in southwest A number of examples for plants, but better documentation exists for all invasive species

61 Lupines in California (native) What is aesthetic?

62 What is aesthetic? Lupines in California (native) Purple loosestrife in CT (exotic)

63 Cultural services Aesthetic beauty, heritage, recreation Maybe the most difficult to quantify or generalize, but local, state and national policy initiatives indicate that invasive [plant] species threaten things widely accepted as important (e.g., boating, hiking, fishing, bird watching).

64 The practicality of invasive plant species and ecosystem services How have invasive species affected ecosystem services? - Significant effects on all categories Can we restore ecosystem services following invasion?

65 The practicality of invasive plant species and ecosystem services How have invasive species affected ecosystem services? - Significant effects on all categories Can we restore ecosystem services following invasion?

66 Restoring ecosystem services Removal of invasive species Manual, chemical, biological methods

67 Restoring ecosystem services Removal of invasive species manual, chemical, biological methods Removal alone is not enough Legacies of invasion exist Legacies can have an impact on ecosystem services (restoring and maintaining) Legacies established during invasive plant species occupancy Legacy effects retained (long) after invasive plant species have vacated

68 Legacies of invasive species Community legacies Changes in nutrient or resource pools

69 Pools vs. fluxes Nitrogen cycle: Pools: Vegetation, soil organic matter, inorganic N Fluxes: Plant uptake, mineralization, nitrification, leaching

70 Legacies of invasive species Community legacies Changes in nutrient or resource pools - N-fixers increase soil N pools - California non-native grasses increase N leaching losses - Tamarix increases sedimentation, narrows stream channels

71 Legacies of invasive species Community legacies Changes in nutrient or resource pools - N-fixers increase soil N stocks - California non-native grasses increase N leaching losses - Tamarix increases sedimentation, narrows stream channels Changes in soil biota

72 Changing soil biotic communities Soil from garlic mustard stands has lower mycorrhizal fungi colonization Soil from garlic mustard stands has lower tree seedling growth Stinson et al. 2006

73 Changing soil biotic communities Soil from garlic mustard stands has lower mycorrhizal fungi colonization Soil from garlic mustard stands has lower tree seedling growth Mechanism Garlic mustard disrupts plantfungi mutualism Stinson et al. 2006

74 Legacies of invasive species Community legacies Changes in nutrient or resource pools - N-fixers increase soil N stocks - California non-native grasses increase N leaching losses - Tamarix increases sedimentation, narrows stream channels Changes in soil biota To be successful, restoration must consider such legacies and their costs to the ecosystem

75 The practicality of invasive plant species and ecosystem services How have invasive species affected ecosystem services? - Significant effects on all categories Can we restore ecosystem services following invasion? - Yes, but must do more than just remove target species - Legacies of invasion may limit restoration

76 Summary Current and Future Directions: Continue to fill knowledge gaps on the processes underlying ecosystem services and impacts by invasive plant species theoretical and practical Evaluate benefits of ecosystem services and trade-offs among management actions related to invasive plant species that affect these services Determine the value of ecosystem services to more accurately direct the decision making process in the management of invasive plant species Incorporate technology to identify and quantify ecosystem services at the landscape scale

77 Acknowledgements Early Career Grant - North Central Regional Center for Rural Development (NCRCRD) Soil and Water Conservation Society