Drought refuge

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A drought refuge is a site that provides permanent

climatic variability
are exacerbated by human activities.

Description

Reliable drought refuges are characterised by the ability to retain sufficient water throughout the drought, having water quality good enough to maintain the life of the ecosystem that are not subject to physical disturbance and that have access to surrounding habitat, so that refugees can recolonise the main habitat when the drought ends.[1]

For

ephemeral lakes when these are inundated.[3][4][5]

"Drought refuge is a secure place persisting through a disturbance with the critical criterion being that after the disturbance the refuge provides colonist to allow populations to recover."[This quote needs a citation]

For some species the refuge is their only water source and is necessary for survival.[6] For birds and invertebrate taxa, the drought refuge is not only necessary for survival but contributes to their reproductive success. Some organisms are able to adapt to the environment when there is a drought, but adapting traits that will be beneficial for survival in a prolonged drought is extremely difficult to accomplish.

Terms refuge and drought

The term

refuge, to define places that protect populations of plants or animals from smaller-scale disturbances, such as fire, flood, storm, or human impacts.[7] Refugia are the habitats or environmental factors that give spatial and temporal resistance and resilience to biotic communities impacted by disturbance.[9] Here negative effects of disturbance are lower than surrounding areas or times.[9] Refugia buffer species long-term, where as, a refuge buffers species short-term.[10]

There are other uses of the term refuge, such as for a wildlife reserve or a place free from predators (predation refuge).[7] A refuge is a place or situation that provides safety or shelter.[7] Here, species are minimally affected by changing climate conditions.[10]

Lack of precipitation causes drying of aquatic ecosystems and leads to a natural disturbance called a drought.[9] In order for organisms to survive a drought, the disturbance must be minimal or there must be a drought refuge available.[9]

Effects of drought

The severity of a disturbance is measured by its intensity, duration, and recovery time.

resistance of a species.[8] Refuge degradation increases mortality for sensitive species during larger disturbance times.[8]

Droughts decrease surface area and volume, while increasing

adaptations that provide refuge.[9]

Hydrological extremes, such as

organisms is another result of droughts.[9][11] Increased organism density leads to resource limitations, movement limitations, increased competition, and increased predation pressure.[9] Droughts also cause changes in food resources and water quality.[11]

Function and importance of drought refuges

Drought refuges protect

semi-arid streams and rivers has increased during the last decade.[7]

The disturbance process and the

resilience, high local mortality with individuals moving back to streams when conditions improve.[9][15][16]

The processes of disturbance, refuge formation, refuge function and recolonization occur at varying temporal and spatial scales.

physicochemical factors as well; contribution is shared.[16] Refuges can be small or large and can be used for short or long periods of time.[9]

Refugia are relative depending on species

adaptations, spatial and temporal scale, and disturbance regime.[9] Many relative influences are unclear as each situation is different.[16] Drought refuges are important for sustaining biodiversity over larger spatial scales.[15]

macroinvertebrate and fish.[15] Differences in longitudinal pattern affect the location and function of perennial water refuges.[7]

Refuge occupancy is predictable based on

intrinsic traits.[15]

There are specific regions (refuges) to which individuals move during a drought, and within these regions there are specific characteristics of sites used as refuges by different species.[12] A species may use more than one type of refuge during its life cycle.[7] A variation in refuge use is caused by topography, individual species susceptibility and response to disturbance.[8] Patterns of refuge use are influenced by disturbance type, species type, patch size, potential occupants and location.[8] These patterns are poorly understood.[16]

Drought refuges form

location, and soil composition are all contributing factors.[16] Heavily shaded pools have colder water, where as lightly shaded pools have increased levels of primary productivity.[16] Large refuges have increased abundance and enrichment and are likely to persist through long disturbances.[8][16]

While used infrequently and often containing only few individuals during normal years, range edges may episodically serve as refuges from extreme weather events or conditions such as drought.[12] During these extreme conditions, survival probability, reproductive success or both is higher at the edge than in the core of its range.[12]

Refuge use is influenced by habitat characteristics, such as hydrolic exchange and

behaviour and physiology.[11] A decline in refuge use is due to decreased effectiveness of mortality reduction and reduced time provided for community recovery which leads to reduced time between disturbances.[8]

Movement into and out of refuge creates predictable fluxes of

chemical conditions are all contributors.[13]

Drought refuges for

macrophytes and zooplankton typically comprise egg and seed banks in med-rivers and are resilient to prolonged drying.[7]

Importance of Refuge Connectivity

dams
, isolated pools), biotic factors (ex: predation, competition), and physicochemical factors (ex: low dissolved oxygen levels).

During smaller scale, shorter term disturbances, populations within refuges are not necessarily cut off from those in other refuges or those in other undisturbed

insects
, refuges on one stream may support recolonization on adjacent streams that are not hydro logically connected, which may also necessitate conservation planning across catchment boundaries.

The drought from 1996 until 2009 had a great impact on the Murray-Darling Basin, in Northern Australia (Murphy and Timbal 2007; Umenhofer et al. 2009). When this drought occurred, it dried the wetlands and water storages (the drought refuge). For many species of birds and fish, the refuge is the only freshwater available. The body of water serves as food and shelter; therefore, it must be conserved. Drought refuges are likely to sustain biodiversity over larger spatial scales such as groups of streams or whole drainage networks. Chester, E. T. and Robson, B. J. (2011), Drought refuges, spatial scale and recolonization by invertebrates in non-perennial streams. Freshwater Biology, 56: 2094–2104.

Different Types of Drought Refuge

A

Mobile species' coping methods include refuge-seeking behavior; they seek habitat patches that relieve physiological stress and reduce mortality.[15] Reliance on dispersal improves resilience to climate change in the short term, but over longer timescales, it will not protect macro invertebrate biodiversity
from landscape-scale refuge degradation.

The hyporheic zone, a region along streambeds where groundwater mixes with surface water,[14] is an important refuge for immobile organisms, like algae. The hyporheic zone protects from freezing, high temperature, and pollution. It reduces displacement, with its relatively stable, slow flow.[11] In a hyporheic zone, free water is retained, and invertebrates remain submerged.[15] The hyporheic zone has been shown to contribute colonists when surface flows recommence.

Perennial waters, whether pools, seeps or flowing sections of streams, have repeatedly been shown to be the major refuges.

taxa
because they require the least investment by the invertebrates.

Threats and conservation

Because

anthropogenic runoff. Consequently, in areas subject to intermittent drought, habitat conservation requires the identification and protection of drought refuges.[2]

invertebrates or by causing anoxia in stream pools and existing environmental degradation of many perennial
water-ways.

Droughts have the ability to reduce agriculture products and be the cause loss of crops and lives. Hence, reserving the refuge is of extreme importance in more ways than one. In order to conserve the drought refuge for these species, action needs to be taken that will effect short term and long term impacts that the drought have on the species that dwell on it for survival. In California, efforts to conserve the drought refuge there, include reserving water when possible. Water conservation is done in order to migrating bird populations (National Wildlife Refuge; March, 1, 2016). The National wildlife refuge also takes part in mowing, disking, spraying and controlled burns. These measures are taken in an effort to stop non-native vegetation from growing; this type of vegetation typically out grows the native when in drought. Thus, allowing for native vegetation to survive during drought, leading to the dependent species to forage on the available vegetation. The clean water act was passed in order to protect the American waters from pollution. Although the act does not protect all waters, it protects many bodies of water. When drought refuges are polluted, they become an even greater danger for the dwelling species. The clean water act is just one step in cleaning waters, and saving drought refuges "(The Clean Water Rule; National Wildlife Organization)."

Continuous threats to the drought refuge conservation include; sedimentation, waterhole pumping, and the lack of the structure of the water, it is not near any other bodies of water. These of course, lead to situations where there is an extreme decrease in water availability. As water availability decreases, it increases the chances for dependent species to die out.

ecosystems.[10] Over-extraction often occurs in areas with surface water scarcity and frequent drought; where groundwater refuges and refugia are most important.[9] Man-made disturbances can mimic the effects of drought, like water withdrawal, and dams.[11] Man-made channel modifications threaten the hyporheic zone
as a refuge.

[10] Groundwater salinization compromises buffering properties. Vegetation clearance, along with irrigation, causes serious issues. Irrigation increases the water table and mobilizes salts, and vegetation clearance allows it to come in contact with water habitats and vegetation. This stresses species not adapted to high salinity. High levels of salinity reduces water uptake in plants, by causing stomatal closure, reducing photosynthesis. Forests undergo decline in areas of high salinity and shallow groundwater depths because these conditions make them more susceptible to droughts. Forests undergo decline in areas of high salinity and shallow groundwater depths making them more susceptible to droughts.

[15] There needs to be an increased focus on conservation efforts.[10] Knowledge of refuge functions is critical for understanding their role in conservation of biodiversity, especially climatically sensitive species.[15] Especially in regions where climate change is increasing the frequency and duration of dry periods.[16] To best conserve species facing extreme weather events, it is necessary to identify conditions ‘pushing’ species, and, more importantly, to identify the refuge sites to which individuals move.[15] Perennially flowing streams and perennial pools may be crucially important for sustaining biodiversity within a mosaic of stream habitats with drier flow regimes.[12] The primary emphasis of drought refuge protection should be on protecting perennial surface waters and range edges within that landscape.[7] Conservation approaches for river systems will need to focus on identifying and conserving refuges together with maintaining refuge connectivity, reducing the impacts of other disturbances on these systems, and sustaining predictable seasonal flow patterns.

[7] Releases from hydroelectricity reservoirs could be used to lower river water temperatures or replenish reaches of formerly perennial flow, thereby creating refuges for river biota.[11] Also, focusing on maintaining groundwater quality is more beneficial than focusing on surface water resources.[10] Re-vegetation can reduce water pollution in ground and surface water, benefitting biodiversity.[7] There is increasing evidence that habitats created by humans, such as canals, ditches, and farm ponds can support freshwater biodiversity and, therefore, have potential to provide refuges.[8] They can prevent larger organisms, like fish, from becoming stranded as water levels decrease.[7] While the preservation of refuges is crucial to provide recolonization sources, it is not sufficient if colonists cannot get from the refuge to habitat patches suitable for colonization.

Conversely, where management of pest species is necessary, controlling them in their drought refuges during droughts may be more cost-effective than broad-scale control at other times. One example of this is controlling

arid and semi-arid regions of Australia.[17]

See also

References

  1. ^ "Refuge habitats". Drought Science. eWater CRC. Retrieved 2011-09-02.
  2. ^ a b Bond, N.R. (2007). Identifying, mapping and managing drought refuges: a brief summary of issues and approaches. eWater Technical Report. eWater Cooperative Research Centre: Canberra. "Archived copy" (PDF). Archived from the original (PDF) on 2009-09-18. Retrieved 2011-09-02.{{cite web}}: CS1 maint: archived copy as title (link)
  3. ^ Anon (2000). "Wetlands as waterbird habitat" (PDF). Water Notes. 5. Water and Rivers Commission, Western Australia. Archived from the original (PDF) on 2011-03-28.
  4. doi:10.1071/mu9870253
    .
  5. ^ "Birds find a refuge". Water Victoria: News and resources. Department of Sustainability and Environment, Victoria. 2008-08-26. Archived from the original on 2011-04-13. Retrieved 2011-09-02.
  6. ^ Lake, P. Sam Drought and Aquatic Ecosystems: Effects and Responses
  7. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z Robson, B. J., Chester, E. T., Mitchell, B. D., & Matthews, T. G. (2013). Disturbance and the role of refuges in mediterranean climate streams. Hydrobiologia, 719(1), 77–91.
  8. ^ a b c d e f g h i j k l m n o p q r s t u v w x Parkos, J. J., Ruetz, C. R., Trexler, J. C. (2011). Disturbance regime and limits on benefits of refuge use for fishes in a fluctuating hydroscape. Oikos, 120(10), 1519-1530.
  9. ^ a b c d e f g h i j k l m n o p q r s Magoulick, D. D., & Kobza, R. M. (2003). The role of refugia for fishes during drought: A review and synthesis. Freshwater Biology, 48, 1186–1198.
  10. ^ a b c d e f g h i j Kath, J., Powell, S., Reardon-Smith, K., El Sawah, S., Jakeman, A. J., Croke, B. F. W., & Dyer, F. J. (2015). Groundwater salinization intensifies drought impacts in forests and reduces refuge capacity. Journal of Applied Ecology, 52, 1116–1125.
  11. ^ a b c d e f g h i j k Stubbington, R. (2012). The hyporheic zone as an invertebrate refuge: A review of variability in space, time, taxa and behavior. Marine and Freshwater Research, 63(4), 293-311.
  12. ^ a b c d e Bateman, B. L., Pidgeon, A. M., Radeloff, V. C., Allstadt, A. J., Akcakaya, H., R., Thogmartin, W. E., Vavrus, S. J., & Heglund, P. J. (2015). The importance of range edges for an irruptive species during extreme weather events. Landscape Ecology, 30(6), 1095-1110.
  13. ^ a b c d e Humphries, P., & Baldwin, D. S. (2003). Drought and aquatic ecosystems: An introduction. Freshwater Biology, 48(7), 1141-1146.
  14. ^ a b c d Robson, B. J., & Matthews, T. G. (2004). Drought refuges affect algal recolonisation in intermittent streams. River Research and Applications, 20(7), 753-763.
  15. ^ a b c d e f g h i j k l m n o p q r s Chester, E. T., & Robinson, B. J. (2011). Drought refuges, spatial scale and recolonisation by invertebrates in non-perennial streams. Freshwater Biology, 56(10), 2094-2104.
  16. ^ a b c d e f g h i j k l m n Pires, D. F., Pires, A. M., Collares, M. J., & Magalhaes, M. F. (2010). Variation in fish assemblages across dry-season pools in a Mediterranean stream: Effects of pool morphology, physicochemical factors and spatial context. Ecology of Freshwater Fish, 19, 74-86.
  17. ^ Berman, D. (2008). "Control of rabbits in arid Australia: destroying the drought refuge". In: Proceedings of the 14th Australasian Vertebrate Pest Conference, 10–13 June 2008, Canberra: 153.
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