Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity

Jarrod KATH, Sue POWELL, K. Reardon-Smith, S El Sawah, Anthony Jakeman, Barry Croke, Fiona DYER

    Research output: Contribution to journalArticle

    2 Citations (Scopus)

    Abstract

    Shallow groundwater aquifers regularly support drought refuges for water-dependent ecosystems. However, many aquifers are impacted by over-extraction and pollution, potentially degrading their ability to support groundwater-fed drought refuges. We investigated the response of groundwater-connected riverine forests to a drought considered equivalent in intensity to those predicted under severe climate change for 2030. The drought's impact was investigated in an area where shallow groundwater resources are heavily exploited and polluted by salinization. We used remotely sensed vegetation productivity (enhanced vegetation index) data from a long-term data set (2000-2011) at 475 riverine forest sites in the Campaspe catchment, south-eastern Australia. Generalized additive mixed models and boosted regression trees were used to model the relationship between groundwater and other environmental covariates with forest change during drought. Models explained up to 44% of the variation in forest change during drought. Forests underwent the greatest declines in areas of high salinity (>6000 µS cm-1) associated with shallow groundwater depths (0-5 m). Conversely, forests in areas of lowest salinity (-1) and groundwater depths of more than 7·5 m showed the least decline during drought. In landscapes where groundwater quality is not compromised, previous studies have shown that shallow groundwater provides important drought refuges and refugia. Here, we show that when groundwater salinization has occurred, forests connected to shallow groundwater are more vulnerable to drought. In effect, salinization reduces the capacity of groundwater-connected habitats to function as drought refuges. Synthesis and applications. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources.
    Original languageEnglish
    Pages (from-to)1116-1125
    Number of pages10
    JournalJournal of Applied Ecology
    Volume52
    Issue number5
    DOIs
    Publication statusPublished - 2015

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    salinization
    refuge
    drought
    groundwater
    catchment
    refugium
    freshwater ecosystem
    revegetation
    water stress
    water resource
    aquifer
    surface water
    salinity
    vegetation index
    groundwater resource
    water

    Cite this

    KATH, Jarrod ; POWELL, Sue ; Reardon-Smith, K. ; El Sawah, S ; Jakeman, Anthony ; Croke, Barry ; DYER, Fiona. / Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity. In: Journal of Applied Ecology. 2015 ; Vol. 52, No. 5. pp. 1116-1125.
    @article{ff7654e9419846df8de77754a02d13fe,
    title = "Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity",
    abstract = "Shallow groundwater aquifers regularly support drought refuges for water-dependent ecosystems. However, many aquifers are impacted by over-extraction and pollution, potentially degrading their ability to support groundwater-fed drought refuges. We investigated the response of groundwater-connected riverine forests to a drought considered equivalent in intensity to those predicted under severe climate change for 2030. The drought's impact was investigated in an area where shallow groundwater resources are heavily exploited and polluted by salinization. We used remotely sensed vegetation productivity (enhanced vegetation index) data from a long-term data set (2000-2011) at 475 riverine forest sites in the Campaspe catchment, south-eastern Australia. Generalized additive mixed models and boosted regression trees were used to model the relationship between groundwater and other environmental covariates with forest change during drought. Models explained up to 44{\%} of the variation in forest change during drought. Forests underwent the greatest declines in areas of high salinity (>6000 µS cm-1) associated with shallow groundwater depths (0-5 m). Conversely, forests in areas of lowest salinity (-1) and groundwater depths of more than 7·5 m showed the least decline during drought. In landscapes where groundwater quality is not compromised, previous studies have shown that shallow groundwater provides important drought refuges and refugia. Here, we show that when groundwater salinization has occurred, forests connected to shallow groundwater are more vulnerable to drought. In effect, salinization reduces the capacity of groundwater-connected habitats to function as drought refuges. Synthesis and applications. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources.",
    author = "Jarrod KATH and Sue POWELL and K. Reardon-Smith and {El Sawah}, S and Anthony Jakeman and Barry Croke and Fiona DYER",
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    KATH, J, POWELL, S, Reardon-Smith, K, El Sawah, S, Jakeman, A, Croke, B & DYER, F 2015, 'Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity', Journal of Applied Ecology, vol. 52, no. 5, pp. 1116-1125. https://doi.org/10.1111/1365-2664.12495

    Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity. / KATH, Jarrod; POWELL, Sue; Reardon-Smith, K.; El Sawah, S; Jakeman, Anthony; Croke, Barry; DYER, Fiona.

    In: Journal of Applied Ecology, Vol. 52, No. 5, 2015, p. 1116-1125.

    Research output: Contribution to journalArticle

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    T1 - Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity

    AU - KATH, Jarrod

    AU - POWELL, Sue

    AU - Reardon-Smith, K.

    AU - El Sawah, S

    AU - Jakeman, Anthony

    AU - Croke, Barry

    AU - DYER, Fiona

    PY - 2015

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    N2 - Shallow groundwater aquifers regularly support drought refuges for water-dependent ecosystems. However, many aquifers are impacted by over-extraction and pollution, potentially degrading their ability to support groundwater-fed drought refuges. We investigated the response of groundwater-connected riverine forests to a drought considered equivalent in intensity to those predicted under severe climate change for 2030. The drought's impact was investigated in an area where shallow groundwater resources are heavily exploited and polluted by salinization. We used remotely sensed vegetation productivity (enhanced vegetation index) data from a long-term data set (2000-2011) at 475 riverine forest sites in the Campaspe catchment, south-eastern Australia. Generalized additive mixed models and boosted regression trees were used to model the relationship between groundwater and other environmental covariates with forest change during drought. Models explained up to 44% of the variation in forest change during drought. Forests underwent the greatest declines in areas of high salinity (>6000 µS cm-1) associated with shallow groundwater depths (0-5 m). Conversely, forests in areas of lowest salinity (-1) and groundwater depths of more than 7·5 m showed the least decline during drought. In landscapes where groundwater quality is not compromised, previous studies have shown that shallow groundwater provides important drought refuges and refugia. Here, we show that when groundwater salinization has occurred, forests connected to shallow groundwater are more vulnerable to drought. In effect, salinization reduces the capacity of groundwater-connected habitats to function as drought refuges. Synthesis and applications. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources.

    AB - Shallow groundwater aquifers regularly support drought refuges for water-dependent ecosystems. However, many aquifers are impacted by over-extraction and pollution, potentially degrading their ability to support groundwater-fed drought refuges. We investigated the response of groundwater-connected riverine forests to a drought considered equivalent in intensity to those predicted under severe climate change for 2030. The drought's impact was investigated in an area where shallow groundwater resources are heavily exploited and polluted by salinization. We used remotely sensed vegetation productivity (enhanced vegetation index) data from a long-term data set (2000-2011) at 475 riverine forest sites in the Campaspe catchment, south-eastern Australia. Generalized additive mixed models and boosted regression trees were used to model the relationship between groundwater and other environmental covariates with forest change during drought. Models explained up to 44% of the variation in forest change during drought. Forests underwent the greatest declines in areas of high salinity (>6000 µS cm-1) associated with shallow groundwater depths (0-5 m). Conversely, forests in areas of lowest salinity (-1) and groundwater depths of more than 7·5 m showed the least decline during drought. In landscapes where groundwater quality is not compromised, previous studies have shown that shallow groundwater provides important drought refuges and refugia. Here, we show that when groundwater salinization has occurred, forests connected to shallow groundwater are more vulnerable to drought. In effect, salinization reduces the capacity of groundwater-connected habitats to function as drought refuges. Synthesis and applications. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources. Currently, there is an emphasis on managing environmental flows to support freshwater ecosystems and associated forests under water stress. However, delivery of environmental water is restricted to areas within a linear stream network and there is often limited capacity to deliver environmental flows during drought. Alternatively, a focus on drought refuges and refugia and processes important for maintaining groundwater quality (e.g. catchment revegetation to reduce shallow groundwater salinization) may better allow drought effects to be managed across a catchment, without directly focusing on highly contested surface water resources.

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