Savanna responses to feral buffalo in Kakadu National Park, Australia

Aaron Petty, Pat Werner, Caroline Lehmann, J Riley, D Banfai, L ELLIOTT

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Savannas are the major biome of tropical regions, spanning 30% of the Earth's land surface. Tree:grass ratios of savannas are inherently unstable and can be shifted easily by changes in fire, grazing, or climate. We synthesize the history and ecological impacts of the rapid expansion and eradication of an exotic large herbivore, the Asian water buffalo (Bubalus bubalus), on the mesic savannas of Kakadu National Park (KNP), a World Heritage Park located within the Alligator Rivers Region (ARR) of monsoonal north Australia. The study inverts the experience of the Serengeti savannas where grazing herds rapidly declined due to a rinderpest epidemic and then recovered upon disease control. Buffalo entered the ARR by the 1880s, but densities were low until the late 1950s when populations rapidly grew to carrying capacity within a decade. In the 1980s, numbers declined precipitously due to an eradication program. We show evidence that the rapid population expansion and sudden removal of this exotic herbivore created two ecological cascades by altering ground cover abundance and composition, which in turn affected competitive regimes and fuel loads with possible further, long-term effects due to changes in fire regimes. Overall, ecological impacts varied across a north-south gradient in KNP that corresponded to the interacting factors of precipitation, landform, and vegetation type but was also contingent upon the history of buffalo harvest. Floodplains showed the greatest degree of impact during the period of rapid buffalo expansion, but after buffalo removal, they largely reverted to their prior state. Conversely, the woodlands experienced less visible impact during the first cascade. However, in areas of low buffalo harvest and severe impact, there was little recruitment of juvenile trees into the canopy due to the indirect effects of grazing and high frequency of prescribed fires once buffalo were removed. Rain forests were clearly heavily impacted during the first cascade, but the long term consequences of buffalo increase and removal remain unclear. Due to hysteresis effects, the simple removal of an exotic herbivore was not sufficient to return savanna systems to their previous state. � 2007 by the Ecological Society of America.
    Original languageEnglish
    Pages (from-to)441-463
    Number of pages23
    JournalEcological Monographs
    Volume77
    Issue number3
    Publication statusPublished - 2007

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    savanna
    savannas
    buffaloes
    national parks
    national park
    herbivore
    grazing
    ecological impact
    alligators
    herbivores
    disease control
    ground cover
    tropical region
    biome
    history
    hysteresis
    carrying capacity
    river
    vegetation type
    landform

    Cite this

    Petty, A., Werner, P., Lehmann, C., Riley, J., Banfai, D., & ELLIOTT, L. (2007). Savanna responses to feral buffalo in Kakadu National Park, Australia. Ecological Monographs, 77(3), 441-463.
    Petty, Aaron ; Werner, Pat ; Lehmann, Caroline ; Riley, J ; Banfai, D ; ELLIOTT, L. / Savanna responses to feral buffalo in Kakadu National Park, Australia. In: Ecological Monographs. 2007 ; Vol. 77, No. 3. pp. 441-463.
    @article{f54577d41dd24103a36a7ff900125656,
    title = "Savanna responses to feral buffalo in Kakadu National Park, Australia",
    abstract = "Savannas are the major biome of tropical regions, spanning 30{\%} of the Earth's land surface. Tree:grass ratios of savannas are inherently unstable and can be shifted easily by changes in fire, grazing, or climate. We synthesize the history and ecological impacts of the rapid expansion and eradication of an exotic large herbivore, the Asian water buffalo (Bubalus bubalus), on the mesic savannas of Kakadu National Park (KNP), a World Heritage Park located within the Alligator Rivers Region (ARR) of monsoonal north Australia. The study inverts the experience of the Serengeti savannas where grazing herds rapidly declined due to a rinderpest epidemic and then recovered upon disease control. Buffalo entered the ARR by the 1880s, but densities were low until the late 1950s when populations rapidly grew to carrying capacity within a decade. In the 1980s, numbers declined precipitously due to an eradication program. We show evidence that the rapid population expansion and sudden removal of this exotic herbivore created two ecological cascades by altering ground cover abundance and composition, which in turn affected competitive regimes and fuel loads with possible further, long-term effects due to changes in fire regimes. Overall, ecological impacts varied across a north-south gradient in KNP that corresponded to the interacting factors of precipitation, landform, and vegetation type but was also contingent upon the history of buffalo harvest. Floodplains showed the greatest degree of impact during the period of rapid buffalo expansion, but after buffalo removal, they largely reverted to their prior state. Conversely, the woodlands experienced less visible impact during the first cascade. However, in areas of low buffalo harvest and severe impact, there was little recruitment of juvenile trees into the canopy due to the indirect effects of grazing and high frequency of prescribed fires once buffalo were removed. Rain forests were clearly heavily impacted during the first cascade, but the long term consequences of buffalo increase and removal remain unclear. Due to hysteresis effects, the simple removal of an exotic herbivore was not sufficient to return savanna systems to their previous state. � 2007 by the Ecological Society of America.",
    keywords = "community response, feral organism, floodplain, grazing pressure, habitat restoration, historical ecology, invasive species, national park, population growth, restoration ecology, ruminant, savanna, World Heritage Site, Alligator Rivers, Australasia, Australia, Kakadu National Park, Northern Territory, Alligator, Bos, Bubalus, Bubalus bubalis",
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    Petty, A, Werner, P, Lehmann, C, Riley, J, Banfai, D & ELLIOTT, L 2007, 'Savanna responses to feral buffalo in Kakadu National Park, Australia', Ecological Monographs, vol. 77, no. 3, pp. 441-463.

    Savanna responses to feral buffalo in Kakadu National Park, Australia. / Petty, Aaron; Werner, Pat; Lehmann, Caroline; Riley, J; Banfai, D; ELLIOTT, L.

    In: Ecological Monographs, Vol. 77, No. 3, 2007, p. 441-463.

    Research output: Contribution to journalArticleResearchpeer-review

    TY - JOUR

    T1 - Savanna responses to feral buffalo in Kakadu National Park, Australia

    AU - Petty, Aaron

    AU - Werner, Pat

    AU - Lehmann, Caroline

    AU - Riley, J

    AU - Banfai, D

    AU - ELLIOTT, L

    PY - 2007

    Y1 - 2007

    N2 - Savannas are the major biome of tropical regions, spanning 30% of the Earth's land surface. Tree:grass ratios of savannas are inherently unstable and can be shifted easily by changes in fire, grazing, or climate. We synthesize the history and ecological impacts of the rapid expansion and eradication of an exotic large herbivore, the Asian water buffalo (Bubalus bubalus), on the mesic savannas of Kakadu National Park (KNP), a World Heritage Park located within the Alligator Rivers Region (ARR) of monsoonal north Australia. The study inverts the experience of the Serengeti savannas where grazing herds rapidly declined due to a rinderpest epidemic and then recovered upon disease control. Buffalo entered the ARR by the 1880s, but densities were low until the late 1950s when populations rapidly grew to carrying capacity within a decade. In the 1980s, numbers declined precipitously due to an eradication program. We show evidence that the rapid population expansion and sudden removal of this exotic herbivore created two ecological cascades by altering ground cover abundance and composition, which in turn affected competitive regimes and fuel loads with possible further, long-term effects due to changes in fire regimes. Overall, ecological impacts varied across a north-south gradient in KNP that corresponded to the interacting factors of precipitation, landform, and vegetation type but was also contingent upon the history of buffalo harvest. Floodplains showed the greatest degree of impact during the period of rapid buffalo expansion, but after buffalo removal, they largely reverted to their prior state. Conversely, the woodlands experienced less visible impact during the first cascade. However, in areas of low buffalo harvest and severe impact, there was little recruitment of juvenile trees into the canopy due to the indirect effects of grazing and high frequency of prescribed fires once buffalo were removed. Rain forests were clearly heavily impacted during the first cascade, but the long term consequences of buffalo increase and removal remain unclear. Due to hysteresis effects, the simple removal of an exotic herbivore was not sufficient to return savanna systems to their previous state. � 2007 by the Ecological Society of America.

    AB - Savannas are the major biome of tropical regions, spanning 30% of the Earth's land surface. Tree:grass ratios of savannas are inherently unstable and can be shifted easily by changes in fire, grazing, or climate. We synthesize the history and ecological impacts of the rapid expansion and eradication of an exotic large herbivore, the Asian water buffalo (Bubalus bubalus), on the mesic savannas of Kakadu National Park (KNP), a World Heritage Park located within the Alligator Rivers Region (ARR) of monsoonal north Australia. The study inverts the experience of the Serengeti savannas where grazing herds rapidly declined due to a rinderpest epidemic and then recovered upon disease control. Buffalo entered the ARR by the 1880s, but densities were low until the late 1950s when populations rapidly grew to carrying capacity within a decade. In the 1980s, numbers declined precipitously due to an eradication program. We show evidence that the rapid population expansion and sudden removal of this exotic herbivore created two ecological cascades by altering ground cover abundance and composition, which in turn affected competitive regimes and fuel loads with possible further, long-term effects due to changes in fire regimes. Overall, ecological impacts varied across a north-south gradient in KNP that corresponded to the interacting factors of precipitation, landform, and vegetation type but was also contingent upon the history of buffalo harvest. Floodplains showed the greatest degree of impact during the period of rapid buffalo expansion, but after buffalo removal, they largely reverted to their prior state. Conversely, the woodlands experienced less visible impact during the first cascade. However, in areas of low buffalo harvest and severe impact, there was little recruitment of juvenile trees into the canopy due to the indirect effects of grazing and high frequency of prescribed fires once buffalo were removed. Rain forests were clearly heavily impacted during the first cascade, but the long term consequences of buffalo increase and removal remain unclear. Due to hysteresis effects, the simple removal of an exotic herbivore was not sufficient to return savanna systems to their previous state. � 2007 by the Ecological Society of America.

    KW - community response

    KW - feral organism

    KW - floodplain

    KW - grazing pressure

    KW - habitat restoration

    KW - historical ecology

    KW - invasive species

    KW - national park

    KW - population growth

    KW - restoration ecology

    KW - ruminant

    KW - savanna

    KW - World Heritage Site

    KW - Alligator Rivers

    KW - Australasia

    KW - Australia

    KW - Kakadu National Park

    KW - Northern Territory

    KW - Alligator

    KW - Bos

    KW - Bubalus

    KW - Bubalus bubalis

    M3 - Article

    VL - 77

    SP - 441

    EP - 463

    JO - Ecological Monographs

    JF - Ecological Monographs

    SN - 0012-9615

    IS - 3

    ER -

    Petty A, Werner P, Lehmann C, Riley J, Banfai D, ELLIOTT L. Savanna responses to feral buffalo in Kakadu National Park, Australia. Ecological Monographs. 2007;77(3):441-463.