Satellite-based annual evaporation estimates of invasive alien plant species and native vegetation in South Africa

Meijninger, W.M.L.; Jarmain, C.

doi:10.4314/wsa.v40i1.12

Cited by 32 publications

(26 citation statements)

References 29 publications

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“…However, a number of species with relatively low biomass (e.g. Chromolaena, Lantana) have been found to have relatively high evapotranspiration rates, comparable to large trees (Meininger and Jarmain, 2014). For this assessment, speciesspecific reduction factors were adopted, building on the initial relationships developed by Scott and Smith (1997) and applied to invading species by Cullis et al (2007) and Mallory et al (2011).…”

Section: Estimating Species-specific Reduction Factorsmentioning

confidence: 99%

Estimates of the impacts of invasive alien plants on water flows in South Africa

Maitre¹,

Forsyth²,

Dzikiti³

et al. 2016

WSA

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The adverse impacts of alien plant invasions on water flows have been a prime motivation for South Africa's Working for Water Programme. The approach used in this study builds on a previous national assessment in 1998 by incorporating factors that limit plant water-use, information from recent research and improved flow reduction models. The total reduction in flows is estimated to be 1 444 million m . The taxon with the greatest estimated impact was wattles (Acacia mearnsii, A. dealbata, A. decurrens) with 34.0% of the total reductions, followed by Pinus species (19.3%) and Eucalyptus species (15.8%). The revised estimate is considered on the low side largely because the extent and impacts of riparian invasions have been underestimated. If the current estimates that 4-6% of Acacia mearnsii, Eucalyptus, Populus and Salix invasions are riparian, are adjusted to a more representative 20%, 50%, 80% and 80%, respectively, the total reductions increase by nearly 70% to ~2 444 million m 3 ·yr −1. Producing these estimates involved a number of assumptions and extrapolations, and further research is needed to provide more robust estimates of the impacts.

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Section: Estimating Species-specific Reduction Factorsmentioning

confidence: 99%

Estimates of the impacts of invasive alien plants on water flows in South Africa

Maitre¹,

Forsyth²,

Dzikiti³

et al. 2016

WSA

View full text Add to dashboard Cite

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“…has transformed the grasslands [13,15], affecting rangeland production. Coordinated efforts of clearing IAPs [40] that have higher water use relative to indigenous vegetation [41] are underway to increase the proportion of water available to maintain other ecosystem services provided by rangelands [42,43]. Figure 2 provides an overview of the processing steps described in this section to perform trend analysis and characterize carbon fluxes (NEE) and water use in the catchments.…”

Section: Methodsmentioning

confidence: 99%

Monitoring Effects of Land Cover Change on Biophysical Drivers in Rangelands Using Albedo

Münch

Gibson²,

Palmer

2019

Land

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This paper explores the relationship between land cover change and albedo, recognized as a regulating ecosystems service. Trends and relationships between land cover change and surface albedo were quantified to characterise catchment water and carbon fluxes, through respectively evapotranspiration (ET) and net primary production (NPP). Moderate resolution imaging spectroradiometer (MODIS) and Landsat satellite data were used to describe trends at catchment and land cover change trajectory level. Peak season albedo was computed to reduce seasonal effects. Different trends were found depending on catchment land management practices, and satellite data used. Although not statistically significant, albedo, NPP, ET and normalised difference vegetation index (NDVI) were all correlated with rainfall. In both catchments, NPP, ET and NDVI showed a weak negative trend, while albedo showed a weak positive trend. Modelled land cover change was used to calculate future carbon storage and water use, with a decrease in catchment carbon storage and water use computed. Grassland, a dominant dormant land cover class, was targeted for land cover change by woody encroachment and afforestation, causing a decrease in albedo, while urbanisation and cultivation caused an increase in albedo. Land cover map error of fragmented transition classes and the mixed pixel effect, affected results, suggesting use of higher-resolution imagery for NPP and ET and albedo as a proxy for land cover.

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“…impact of clouds, resolution of images in time and space, requirements for verification on the ground), but also the potential to estimate the water resource impacts of a wide range of invasive alien plants in a consistent manner over a large area, and compare them with other land cover classes (Gibson et al 2013;Meijninger and Jarmain 2014;van Niekerk et al 2018). The only study of this type thus far found that the annual evaporation from areas with invading species was greater than from adjacent areas of natural vegetation across both the Western Cape and KwaZulu-Natal (Meijninger and Jarmain 2014). This is consistent with the generally greater water-use observed in the species and stand level studies described above and a promising development.…”

Section: Extrapolating To Larger Spatial and Longer Temporal Scalesmentioning

confidence: 99%

Impacts of Plant Invasions on Terrestrial Water Flows in South Africa

Maitre

Blignaut

Clulow

et al. 2020

Biological Invasions in South Africa

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Considerable advances have been made since the first estimates of the impacts of invasive alien plants on water resources in the early 1990s. A large body of evidence shows that invasive alien plants can increase transpiration and evaporation losses and thus reduce river flows and mean annual runoff. Riparian invasions, and those in areas where groundwater is accessible, have 1.2-2 times the impact of invasions in dryland areas. The magnitude of the impacts is directly related to differences between the invading species and the dominant native species in size, rooting depth and leaf phenology. Information on the impacts has been successfully used to compare the water use of invasive plants and different land cover classes, to quantify the water resource benefits of control measures, and to prioritise areas for control operations. Nationally, the impacts of invasive alien plants on surface water runoff are estimated at 1.44-2.44 billion m 3 per year. The most affected primary catchments (>5% reduction in mean annual runoff) are located in the Western and Eastern Cape, and KwaZulu-Natal. If no remedial action is taken, reductions in surface water runoff could increase to 2.59-3.15 billion m 3 per year, about 50%

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Satellite-based annual evaporation estimates of invasive alien plant species and native vegetation in South Africa

Cited by 32 publications

References 29 publications

Estimates of the impacts of invasive alien plants on water flows in South Africa

Estimates of the impacts of invasive alien plants on water flows in South Africa

Monitoring Effects of Land Cover Change on Biophysical Drivers in Rangelands Using Albedo

Impacts of Plant Invasions on Terrestrial Water Flows in South Africa

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