David C Le Maitre

David C Le Maitre
Council for Scientific and Industrial Research, South Africa | CSIR · Natural Resources and the Environment Research Area

PhD Botany (ecology), UCT

About

151
Publications
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Introduction
My current research focuses on the impacts of land cover change, including invasions, on water fluxes and water quality and ways of using this information to prioritise management interventions and increase the efficacy and sustainability of investments in invasive plant control. I guided and later led studies on the delineation and development of Strategic Water Source Areas for South Africa and for two river systems in Mozambique. See the Green Book (https://greenbook.co.za/)

Publications

Publications (151)
Chapter
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 gro...
Chapter
Full-text available
Thousands of plant species have been introduced, intentionally and accidentally, to South Africa from many parts of the world. Alien plants are now conspicuous features of many South African landscapes and hundreds of species have naturalised (i.e. reproduce regularly without human intervention), many of which are also invasive (i.e. have spread ov...
Article
A key motivation for managing invasive alien plant (IAP) species is their impacts on streamflows, which, for the wetter half of South Africa, are about 970 m3∙ha−1∙a−1 or 1 444 mill. m3∙a−1 (2.9% of naturalised mean annual runoff), comparable to forest plantations. However, the implications of these reductions for the reliability of yields from lar...
Article
A key motivation for managing invasive alien plant (IAP) species is their impacts on streamflows, which, for the wetter half of South Africa, are about 970 m 3 •ha −1 •a −1 or 1 444 mill. m 3 •a −1 (2.9% of naturalised mean annual runoff), comparable to forest plantations. However, the implications of these reductions for the reliability of yields...
Article
Remote sensing tools are becoming increasingly important for providing spatial information on water use by different ecosystems. Despite significant advances in remote sensing based evapotranspiration (ET) models in recent years, important information gaps still exist on the accuracy of the models particularly in arid and semi-arid environments. In...
Technical Report
Full-text available
The Knysna Fires in June 2017 were the most destructive fires recorded in South Africa. This report, commissioned by Santam, synthesises technical reports by the Research Alliance for Disaster and Risk Reduction (RADAR), the Council for Scientific and Industrial Research (CSIR) and Stellenbosch University's Fire Engineering Research Unit on the les...
Article
Full-text available
Many rivers in the southern coastal region of the Western Cape Province, South Africa, are known to be in a poor state. Since the 1990s, the river water quality of this coastal region has been affected by increasing populations and by intensifying land use activities. Simplified risk assessment approaches are critical to identify in a timely manner...
Article
The success of different rehabilitation treatments following surface mining on the arid west coast of South Africa was assessed. Treatments consisting of one or a combination of topsoil addition, plant translocation and seeding were applied to experimental rehabilitation sites in 2001, while the treatment of another site in 2008 combined all three...
Article
We analyse the impact of failing to control invasive alien plants (IAPs) on the water supply to the Berg River and De Hoop Dams, in other words, the opportunity cost of not clearing IAPs in these two catchments. To do this we used models to assess and compare the impact of current and future invasions on inflows into the dams. Although the clearing...
Article
Full-text available
Invasive alien plants (IAPs) pose a serious threat to the already limited water resources in dry countries like South Africa which are facing increasing water shortages. Much of South Africa is expected to get drier in future due to climate change. In addition, the future climatic conditions are also predicted to accelerate the rate at which IAPs w...
Article
Full-text available
Alien species can have major ecological and socioeconomic impacts in their novel ranges and so effective management actions are needed. However, management can be contentious and create conflicts, especially when stakeholders who benefit from alien species are different from those who incur costs. Such conflicts of interests mean that management st...
Article
Strategic water source areas are those areas that have a relatively high natural runoff in the region of interest, which is made accessible for supporting the region’s population or economy. These areas contribute substantially to development needs, often far away from the source. This disconnect between ecosystem service supply and use means that...
Article
Prosopis spp., (or Mesquite), is a desert adapted woody weed which has invaded large parts of arid and semi-arid regions. It has a characteristic deep tap root, and forms dense impenetrable thickets along river banks, flood plains, and seasonal water courses. Several studies have quantified the water use by Prosopis, but there is limited informatio...
Conference Paper
In many countries around the world the most damaging invasive plant species are grasses. However, the group has received little attention in South Africa. In response to this information deficiency on a group with high invasion potential we established a National Working Group on Alien Grasses in 2013. One of the main goals of the group so far h...
Chapter
Full-text available
This chapter is organized around the concept of ecohydrological processes that are explicitly tied to ecosystem services. Ecosystem services are benefits that people receive from ecosystems. We focus on (1) the regulating services of water distribution, water purification, and climate regulation; (2) the supporting services of water and nutrient cy...
Article
Background: In many countries around the world, the most damaging invasive plant species are grasses. However, the status of grass invasions in South Africa has not been documented recently. Objectives: To update Sue Milton’s 2004 review of grasses as invasive alien plants in South Africa, provide the first detailed species level inventory of alie...
Chapter
Disturbances, or changes in disturbance regimes, can promote invasions, but invasives can also be seen as drivers of disturbances. Non-native species can either change an existing disturbance regime or introduce disturbance regimes that are novel to the invaded system. Changes in disturbance regimes can be triggered if non-natives act as biotic dis...
Article
Full-text available
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...
Article
Background Prosopis species have been introduced to many areas outside their native range to provide benefits to local communities. Several Prosopis species and their hybrids (hereafter “mesquite”) have, however, become naturalised and invasive and now generate substantial costs. Management options are limited because of the complex conflicts of in...
Conference Paper
Full-text available
Groundwater is a vital source of water for many communities in South Africa and elsewhere. Besides the changing climate, rapidly spreading invasive alien plants with deep roots e.g. Prosopis spp pose a serious threat to this water source. Dense impenetrable thickets of Prosopis occur in the drier parts of the country mainly along river channels in...
Article
Valley-bottom wetlands are valuable assets as they provide many ecosystem services to mankind. Despite their value, valley-bottom wetlands are often exploited and land-use/land-cover (LULC) change results in trade-offs in ecosystem services. We coupled physically based hydrological modeling and spatial analysis to examine the effects of LULC change...
Article
Full-text available
There have been many studies of the diverse impacts of invasions by alien plants but few have assessed impacts on water resources. We reviewed the information on the impacts of invasions on surface runoff and groundwater resources at stand to catchment scales and covering a full annual cycle. Most of the research is South African so the emphasis is...
Article
Full-text available
Many Prosopis species have been introduced to South Africa; some taxa and their hybrids have naturalised and become widespread invasive trees. These invasions have detrimental effects on biodiversity, ecosystem services and human livelihoods. Although several studies have documented these impacts, the studies have been limited to single sites or re...
Article
Invasive alien trees impact the environment and human livelihoods. The human dimensions of such invasions are less well understood than the ecological aspects, and this is hindering the development of effective management strategies. Semi-structured interviews were undertaken to investigate the knowledge and perceptions of Prosopis between differen...
Article
Woody invasive alien plants (IAPs) are a threat to South Africa's water resources, biodiversity and land productivity. The impacts of IAPs were the main reason for the South African government to embark on a natural resource management public works programme called Working for Water (WfW), which was aimed at controlling IAPs in a cost-effective yet...
Article
Full-text available
Invasive species cause ecological, economic and social impacts and are key driver of global change. This is the case for the genus Prosopis (mesquite; Fabaceae) where several taxa are among the world's most damaging invasive species. Many contentious issues ("conflicts of interest") surround these taxa, and management interventions have not yet sus...
Article
Full-text available
Communities worldwide are increasingly affected by natural hazards such as floods, droughts, wildfires and storm-waves. However, the causes of these increases remain underexplored, often attributed to climate changes or changes in the patterns of human exposure. This paper aims to quantify the effect of climate change, as well as land cover change,...
Article
Full-text available
Aspalathus linearis (Burm. f.) R. Dahlgren (rooibos) is endemic to the Fynbos Biome of South Africa, which is an internationally recognized biodiversity hot spot. Rooibos is both an invaluable wild resource and commercially cultivated crop in suitable areas. Climate change predictions for the region indicate a significant warming scenario coupled w...
Article
Full-text available
Many studies have investigated the water relations of indigenous plants in the fynbos shrublands of the Cape, South Africa. These have mainly focused on understanding the mechanisms by which individual plant species respond to droughts, the frequency and severity of which is expected to increase due to climate change. However, comparatively little...
Article
Land and water resource issues typically fall under separate governance systems. For example, agricultural policy regulates land-cover change while water departments regulate water quality. However, land-use changes can directly affect water resources. Water flow regulation is a key service which is affected by changes in land-cover but its dynamic...
Chapter
Full-text available
The relationships between weather/climate conditions and fire through the analysis of historical meteorological data and fire records were investigated using different algorithms and methodologies at several scales, from the Euro-Mediterranean level, through national, NUT02, and local scale. In spite of the use of such a wide range of methodologies...
Article
The article explores the rationale behind the ecological reserve, and links this to the concepts of ecosystem services and ecological infrastructure. The role of ecosystems in regulating water quality led the drafters of the Water Law Principles in 1996 and the 1997 Water Policy to recognize that maintaining water quality required maintaining the e...
Article
This paper describes the first step in developing an approach to fire risk assessment aimed at balancing the reduction of risks to lives and livelihoods and maintaining fire regimes which protect ecosystem biodiversity and function in fire-prone ecosystems. Wildfires pose a major hazard to people's lives, livelihoods and ecosystems in South Africa...
Book
Securing sufficient and reliable water supply is a priority for many countries worldwide, but their efforts are hindered by widespread landscape degradation and uncertainty around future climate change. We used historical aerial photographs and mapping techniques to investigate how a South African landscape has changed over the past century. The Kr...
Technical Report
Full-text available
The degradation of ecosystems, mainly driven by human-induced land transformation, has reached unprecedented levels at a global scale and has been well documented (Wake and Vredenburg 2008; Estes et al. 2011; TEEB 2011). Various studies have indicated the unsustainability of the prevailing situation and the need for a rapid, sustained and large-sca...
Article
Self-established stands of alien invasive pine trees are common in many parts of South Africa and elsewhere. They mainly invade non-riparian settings but sometimes invade riparian habitats. There are clear visual differences in the physical attributes of trees that occupy riparian and non-riparian zones. We have little information whether the diffe...
Article
Full-text available
Can markets assist by providing support for ecological restoration, and if so, under what conditions? The first step in addressing this question is to develop a consistent methodology for economic evaluation of ecological restoration projects. A risk analysis process was followed in which a system dynamics model was constructed for eight diverse ca...
Article
A recent review by Dormann et al. (2012, Journal of Biogeography, 39, 2119-2131) has proposed that methods for the modelling of species distributions be considered as a continuum. We disagree with this thesis, and contend that attempting to present the diverse range of methods as a continuum is unhelpful and ultimately not convincing. It adds to th...
Article
Several Prosopis species have been introduced into South Africa in the last century and many of them have become invasive. This study investigates the water relations, effects of clearing, and the seasonal dynamics of groundwater use by invasive Prosopis trees. The trees were growing on deep sandy soils in the floodplain of an episodic river in the...
Article
Communities worldwide are increasingly affected by natural hazards such as floods, droughts, wildfires and storm-waves. However, the causes of these increases remain underexplored, often attributed to climate changes or changes in the patterns of human exposure. This paper aims to quantify the effect of climate change, as well as land cover change,...
Article
Full-text available
Petitpierre et al. (Reports, 16 March 2012, p. 1344) conclude that niche shifts are rare for terrestrial plant invaders and that this justifies the use of correlative modeling to project species geographic ranges for biological invasions and climate change. We draw attention to the limitations of their conceptual assumptions and the importance of n...
Article
Mesquite (Prosopis species) were introduced to South Africa to provide fodder and shade for livestock, but some have become invasive, impacting on water and grazing resources. Mesquite’s net economic effects are unclear and their unequal distribution leads to conflict. We estimated the value of mesquite invasions in the Northern Cape Province for d...
Article
Full-text available
Regional and global scale ecosystem service assessments have demonstrated the socioeconomic value of protecting biodiversity and have been integrated into associated policy. Local government decision makers are still unsure of the applicability, return on investment, and usefulness of these assessments in aiding their decision making. Cape Town, a...
Article
Invasive alien plants (IAPs) impose significant social costs on the population of the Agulhas Plain region in South Africa due to their adverse impacts on ecosystem goods and services (decreased water supply and increased fire risk). While the cost of clearing IAPs is considerable, this paper assesses opportunities to reduce some of the social and...
Article
Full-text available
We review the current state of knowledge of quantified impacts of invasive alien plants on water quality, with a focus on South Africa. In South Africa, over 200 introduced plant species are regarded as invasive. Many of these species are particularly prominent in riparian ecosystems and their spread results in native species loss, increased biomas...
Article
Invasions by alien plants are a significant threat to the biodiversity and functioning of ecosystems and the services they provide. The South African Working for Water program was established to address this problem. It needs to formulate objective and transparent priorities for clearing in the face of multiple and sometimes conflicting demands. Th...
Article
A spatial assessment was conducted in the semi-arid area of South Africa, to: (1) identify priority areas for the conservation of river and groundwater ecosystems; (2) examine surface and groundwater quality for human consumption and (3) investigate the rehabilitation of degraded areas to highlight ‘win-win’ situations for both environmental and hu...
Article
Full-text available
Aim The biophysical impacts of invasive Australian acacias and their effects on ecosystem services are explored and used to develop a framework for improved restoration practices. Location South Africa, Portugal and Chile. Methods A conceptual model of ecosystem responses to the increasing severity (density and duration) of invasions was developed...
Article
Aim A range of approaches and philosophies underpin national-level strategies for managing invasive alien plants. This study presents a strategy for the management of taxa that both have value and do harm. Location South Africa. Methods Insights were derived from examining Australian Acacia species in South Africa (c. 70 species introduced, mostly...
Article
Aim Investigate the relative abilities of different bioclimatic models and data sets to project species ranges in novel environments utilizing the natural experiment in biogeography provided by Australian Acacia species. Location Australia, South Africa. Methods We built bioclimatic models for Acacia cyclops and Acacia pycnantha using two discrimin...
Article
Arid regions are home to unique fauna, flora, and vulnerable human populations, and present a challenge for sustainable land-use management. We undertook an assessment and valuation of three key services, grazing, tourism and water supply in the arid Succulent Karoo biome in western South Africa - a globally recognised biodiversity hotspot. We were...
Article
a b s t r a c t Arid regions are home to unique fauna, flora, and vulnerable human populations, and present a challenge for sustainable land-use management. We undertook an assessment and valuation of three key services, grazing, tourism and water supply in the arid Succulent Karoo biome in western South Africa -a globally recognised biodiversity h...