T.D. Wassenaar

T.D. Wassenaar
The Namibia University of Science and Technology · Agriculture and Natural Resources Sciences

PhD

About

33
Publications
9,007
Reads
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556
Citations
Introduction
The way in which plants access, utilise and lose water is a key driver of the dynamics of dryland ecosystems. In my research I am trying to understand native plant adaptations to periodic water scarcity and how these adaptations may affect biodiversity conservation, ecological restoration of degraded land and rangeland health in the context of a changing climate. I am particularly interested in social-ecological systems that show threshold behaviour that makes them vulnerable to global change.
Additional affiliations
July 2018 - present
The Namibia University of Science and Technology
Position
  • Professor (Associate)
Description
  • I teach Animal Health to undergraduate students in the Agriculture stream, as well as Ecology and Restoration Ecology to Natural Resources students. I also supervise Masters and PhD students in theor projects a range of topics around ecology and I am Coordinator of the PhD Programmes in the Faculty of Natural Resource and Spatial Sciences..
May 2010 - June 2018
Gobabeb Namib Research Institute
Position
  • Project Manager
Description
  • Coordination of all internal and external research at the Gobabeb Centre. Head of the Namib Ecological Restoration and Monitoring Unit that specialised in biodiversity management and monitoring services for the mining sector.
March 2005 - June 2018
African Wilderness Restoration
Position
  • Managing Director
Description
  • I headed up a consultancy that provided environmental management services, including biodiversity impact assessments, conservation management plans and ecological restoration planning and implementation projects.
Education
January 2000 - November 2004
University of Pretoria
Field of study
  • Zoology/Ecology
July 1994 - June 1997
University of Pretoria
Field of study
  • Zoology/Ecology
January 1992 - December 1992
University of Pretoria
Field of study
  • Wildlife Management

Publications

Publications (33)
Article
Full-text available
Deserts have been predicted to be one of the most responsive ecosystems to global climate change. In this study, we examine the spatial and demographic response of a keystone endemic plant of the Namib Desert ( Welwitschia mirabilis ), for which displacement and reduction of suitable climate has been foreseen under future conditions. The main aim i...
Article
One of the most recognizable icons of the Namib Desert is the endemic gymnosperm Welwitschia mirabilis. Recent studies indicated that climate change may seriously affect populations in the northern Namibia subrange (Kunene region), but their extinction risk has not yet been assessed. In this study, we apply IUCN criteria to define the extinction ri...
Preprint
Full-text available
One of the most recognisable icon of the Namib Desert is the endemic gymnosperm Welwitschia mirabilis . Recent studies indicated that climate change may seriously affect populations in the northern Namibia subrange (Kunene region) but their extinction risk has not yet been assessed. In this study, we apply IUCN criteria to define the extinction ris...
Preprint
Full-text available
Climate change represents an important threat to global biodiversity and African ecosystems are particularly vulnerable. Recent studies predicted substantial variations of climatic suitability for Welwitschia mirabilis under future conditions. Latitudinal/altitudinal range shifts are well-known responses to climate change but not coherent patterns...
Article
Full-text available
The future of fog‐dependent habitats under climate change is unknown but likely precarious; many have experienced recent declines in fog. Fog‐dependent deserts particularly will be threatened, because, there, fog can be the main water source for biota. We review the interactions between fog and fauna of the Namib Desert, about which there is 50 yr...
Article
Full-text available
An intensive observation period was conducted in September 2017 in the central Namib, Namibia, as part of the project Namib Fog Life Cycle Analysis (NaFoLiCA). The purpose of the field campaign was to investigate the spatial and temporal patterns of the coastal fog that occurs regularly during nighttime and morning hours. The fog is often linked to...
Article
Species with highly restricted ranges are disproportionately at risk of extinction, particularly where habitat loss occurs as a result of mining. Post‐mining restoration of rare species populations is considered as an appropriate response to counter such threats, but requires a careful, evidence‐based and information‐driven approach. The economical...
Article
Full-text available
Welwitschia mirabilis is a long-lived evergreen in the hyperarid Namib Desert; at our study site, rainfall is rare (MAP=31 mm), groundwater deep (57-75 m), and fog frequent (50-90 events y-1). By examining root architecture in relation to soil moisture and analysing the isotopic composition of hydrogen and oxygen of plant and soil water, we establi...
Article
Full-text available
Knowledge of the thermal ecology of a species can improve model predictions for temperature-induced population collapse, which in light of climate change is increasingly important for species with limited distributions. Here, we use a multi-faceted approach to quantify and integrate the thermal ecology, properties of the thermal habitat, and past a...
Poster
Full-text available
Considering projected climate and socio-economic development for Southern Africa, a major challenge in southern Africa is to find mechanisms to adapt to climate change and to secure water at sufficient quality and quantity for both, human well-being and the stability of ecosystem functions and services. Many countries of southern Africa face inadeq...
Article
Full-text available
Fog is a characteristic feature of the Namib Desert and is essential to life in this fog dependent system. It is often acknowledged that advective fog from the ocean is the dominant fog type over the Namib Desert fog-zone but recent evidence suggests that other fog types occur in this area. Knowledge of the existence and spatial distribution of dif...
Article
Science education and outreach for sustainable development in arid Namibia encompasses a wide range of topics referring to economic, social and environmental issues. This paper reviews selected programmes implemented at Gobabeb over the past several decades as case studies in effective and innovative education and outreach. Programmes at Gobabeb co...
Article
Successional processes should increase habitat complexity, and increase resources available for forest-associated species. However, according to the theory of Island Biogeography, the size, amount of edge, and isolation of a habitat patch will influence the probability of successful colonization. If this is true for restoring patches of coastal dun...
Chapter
Full-text available
Coastal dune forests in northern KwaZulu-Natal, South Africa, are continually exposed to natural and man-induced disturbances that usually initiate ecological succession (van Aarde et al. 1996a; Mentis and Ellery 1994). This succession is associated with temporal and spatial changes in vegetation structure that influence habitat suitability and ult...
Article
The recovery of an ecosystem in response to a restoration program that relies on natural processes may be characterized by heterogeneous changes in species composition and structure. In most cases, such variability is natural and should even be welcomed. However, variability that arises from a specific restoration site, as opposed to randomly from...
Article
Full-text available
Recent changes in the climate of the sub-Antarctic may influence the number of house mouse (Mus musculus sensu lato) living on islands in the region. An increase in mouse numbers, as conditions became milder, could amplify the effects of climate change on native prey species. However, we have no direct evidence of the influence of climate on mouse...
Article
Full-text available
Coastal dune forest covers approximately 1% of the land area of KwaZulu-Natal, South Africa. It is a habitat type seriously threatened from human population pressure and development. During 1995, spiders were sampled from the herbaceous layer of coastal dune forests at Richards Bay, KwaZulu-Natal, using sweep nets. Four stands were sampled in rehab...
Article
The rehabilitation of disturbed ecosystems through ecological succession should lead to the recovery of indigenous biological assemblages typical of a region. However, rehabilitation may give rise to unusual successional pathways and lead to atypical assemblages. We compared millipede assemblages along a chronosequence of habitats developing in res...
Article
Do communities return to their former state when we disturb them? The answer is ''surely not always,'' since some disturbances may be so devastating that recovery will be impossible. If communities do recover, then how fast is that recovery? Do different subsets of species return at the same rate? Is that rate a simple exponential recovery— meaning...
Article
Full-text available
The structure and composition of the soil micro-arthropod communities of five postmining rehabilitating sites (between 1 and 24 years after rehabilitation) are compared with that of an undisturbed dune forest benchmark. We extracted soil micro-arthropods (Acari and insects) with a modified Berlese–Tullgren funnel and used soil carbon, calcium, pota...
Article
Full-text available
Abstract House mice (Mus domesticus L.) have been present on sub-Antarctic Marion Island since the early 1800s. Several authors have suggested that an increase in mice density as a result of a general warming trend in the sub-Antarctic climate from the 1960s has led to a decline in invertebrate biomass and abundance. These suggestions have been sup...
Article
We investigated the responses of the ground vegetation in a 17-year-old coastal dune forest plant community to four levels of experimentally applied livestock grazing (three grazing levels and one ungrazed control) from May 1994 to March 1996. The effects of grazing were apparently subordinate to site-specific intrinsic vegetation change and there...
Article
The rehabilitation program conducted by Richards Bay Minerals (RBM) of areas exposed to opencast surface mining of sand dunes north of Richards Bay (28°43'S, 32°12'E) on the coast of northern KwaZulu-Natal Province commenced 16 years before this study and has resulted in the development of a series of known-aged stands of vegetation. By assuming th...

Questions

Questions (3)
Question
We have been using nitrogen to measure large numbers (>1000) of stem water potentials. The cost of N is becoming a limiting factor, so we have been debating other options, cheapest of which is normal air. The manual of the Model 1000 Scholander (PMS Instrument Co.) does not make reference to other gas sources, nor does it say whether it can take only N or not.
Question
We are using iButtons for our research. Most of them are now three years old, but have not been used for longer than a total of a few days each during this period. I want to deploy them for another two years in the field. Curiously the manual has no reference to the battery status, or whether one can still read the data if the battery runs out before you retrieve them.
Question
When I did most of my graduate research, Quattro Pro ruled the roost at our University. Consequently, almost all the macros and statistical analysis sheets that I developed, are in the various QP formats: .wb1, .wb2,. wb3, even some in the old DOS-based .wq1 format. Since then Excel has of course more or less completely taken over as the spreadsheet of choice. Unfortunately, it does not recognize any of the QP formats. Very frustrating, because there is some valuable stuff in there. Does anybody know how I can recover the data from these QP files?

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Projects

Projects (5)
Project
In this project we are trying to improve our understanding of the dynamics of key physiological indicators of plant health as these are affected by season and different river hydrologies. Amongst others, we are trying to define the upper and lower limits within which these parameters vary in natural settings, as well as the critical lower thresholds beyond which recovery becomes less likely. Our focus is on the riparian trees of Namibian ephemeral rivers, whose undergound water resources are much in demand for towns and industry. We hope our research will provide the basis for the monitoring of tree health, to enable earlier warning of environmental impacts to the riparian ecosystems by abstraction of water for human use.