Trinity Western University

Faculty Directory

David Clements, Ph.D.

Professor of Biology

  • Biography

    David Clements is a Professor of Biology and Environmental Studies.  He has taught at TWU since 1994, teaching in the areas of ecology and botany, including field courses in plant ecology in the Gulf Islands off the BC coast and in the Hawaiian islands. He supervises research and restoration at TWU’s field sites including sites in Langley and on Salt Spring Island. He was a founding board member of A Rocha Canada, a national Christian conservation organization and has also served on the board of the Langley Environmental Partners Society, The Langley Field Naturalists and the Salmon River Enhancement Society. He researches weed biology and ecology and is currently the President of the Canadian Weed Science Society. Clements has published more than 50 papers in scientific journals and is currently an editor for two journals: Weed Research and Pacific Science. Clements initiated the series “Biology and impacts of Pacific Island Invasive Species” in the Journal Pacific Science (Clements and Daehler 2007) and continues to serve as the editor for the series.  

     Since 2010 Clements has been invited to participate in annual exchanges with the Yunnan Academy of Agricultural Sciences to study and other invasive weeds in China. He writes a monthly column for the Langley Times called “The Green Beat.” His TWU blog can be found at

    China1 China2


     Clements grew up in Ontario, and completed his Ph.D. at Queen’s University on integrated pest management in apple orchards.  During his post-doc at University of Guelph, Clements continued to apply ecological principles to pest management, this time focusing on weeds.  He lives in Walnut Grove with his wife and four sons, who are growing like weeds. Clements is very interested in the ethics of weed science and larger questions around bioethics and the potential for a Christian theology of environmental stewardship to bring to humanity a deeper, more holistic commitment to caring for the earth.



  • Education

    B.Sc., University of Western Ontario, London, Ont., Canada 1986
    Ph.D., Queen's University, Kingston, Ont., Canada 1991

  • Recent Publications

    1. Clements, D. R. 2013. Translocation of rare plant species to restore Garry oak ecosystems in western Canada: challenges and opportunities. Botany 91(5): 283-291.

    2. Steensma K.M.M., Clements, D.R., Wood, J.R., Van Dragt, R., and Lowe, B. 2013. Stewarding the gift of land: Christian campuses as land management models. Perspectives on Science and Christian Faith. 65(2): 104-115.

    3. Clements, D. R., and DiTommaso, A. 2012. Predicting weed invasion in Canada under climate change: evaluating evolutionary potential. Can. J. Plant Sci. 92: 1013-1020.

    4. Clements, D. R. and Atwood, L. B. 2012. Protecting Ecosystems from Underground Invasions - Seed Bank Dynamics in a Semi-Arid Shrub-Steppe, Diversity of Ecosystems, Prof. Mahamane Ali (Ed.), ISBN: 978-953-51-0572-5, InTech, Available from:

    5. Darbyshire, S. J., Francis, A., DiTommaso, A. and Clements, D. R. 2012. The Biology of Canadian weeds. 150. (L.) Raf. ex DC. Can. J. Plant Sci. 92: 729-746.

    6. Stopps, G. J., White, S. N., Clements, D. R. and Upadhyaya, M. K. 2011. The Biology of Canadian weeds. 149. L. Can. J. Plant Sci. 91: 1037-1052.

    7. Clements, D.R. and DiTommaso, A. 2011. Climate change and weed adaptation: can evolution of invasive plants lead to greater range expansion than forecasted? Weed Res. 51: 227-240.

    8. Francis, A., Darbyshire, S.J., Clements, D. R. and DiTommaso, A. 2011. The Biology of

    9. Canadian Weeds. 146. L. Can. J. Plant Sci. 91: 553-569.

    10. Clements, D.R., Luginbill, S., Jordan, D.A., Van Dragt, R., and Pelant, R. 2011. Techniques to promote Garry oak seedling growth and survival in areas with high levels of herbivory and competition. Northwest Sci. 85: 172-181.

    11. Dennehy, C., Alverson, E.R., Anderson, H.E., Clements, D.R., Gilbert, E.R., and Kaye, T.N. 2011. Management strategies for invasive plants in Pacific Northwest prairies, savannas, and oak  woodlands. Northwest Sci.85: 329-351.

    12. Clements, D.R. and Scott, L. 2011. Weed invasion of the Montane Cordillera Ecozone.

    13. Assessment of Species Diversity in the Montane Cordillera Ecozone. G.G.E. Scudder and I.M. Smith. Royal British Columbia Museum. Pages 1-29.

    14. Gonzales, E.K. and Clements, D.R. 2010. Plant community biomass shifts in response to mowing and fencing in invaded oak meadows with non-native grasses and abundant ungulates. Restoration Ecology 18: 753-761.

    15. DiTommaso, A., Clements, D. R., Darbyshire, S. J. and Dauer, J. T. 2009.  The Biology of Canadian Weeds 143. L.  Can. J. Plant Sci. 89: 977-992.

    16. Qaderi, M. M., Clements, D. R. and Cavers, P. B. 2009.  The Biology of Canadian Weeds 139.  L.  Can. J. Plant Sci. 89: 169-189.

    17. Feenstra, K. R. and Clements, D. R. 2008. Biology and impacts of Pacific Island invasive species. 4. , Golden Crownbeard (Magnoliopsida: Asteraceae).  Pacific Science 62: 161-176.

    18. Clements, D. R., Feenstra, K. R., Jones, K. and Staniforth, R. 2008.  The biology of invasive plants in Canada 9.  Royle.  Can. J. Plant Sci. 88: 403-417.

    19. Clements, D. R. and Catling, P. 2007.  Invasive species issues in Canada – How can ecology help? Can. J. Plant Sci.87:989-992.

    20. Clements, D. R. and Darbyshire, S. J. eds. 2007. Invasive plants: Inventories, strategies and action. Topics in Canadian Weed Science, Volume 5. Sainte Anne de Bellevue, Québec: Canadian Weed Science Society – Société canadienne de malherbologie. 165 pp.

    21. Clements, D. R. and Darbyshire, S. J. 2007.  Introduction. Pages 1-4 Invasive plants: Inventories, strategies and action. Topics in Canadian Weed Science, Volume 5. Sainte Anne de Bellevue, Québec: Canadian Weed Science Society – Société canadienne de malherbologie. 165 pp.

    22. Clements, D.R., Krannitz, P.G. and Gillespie, S.M. 2007. Seed banks of invasive and native plant species in a semi-desert shrub-steppe with varying grazing histories. Northwest Science 81: 37- 49.

    23. Clements, D.R. and Daehler, C. 2007.  Introducing a new series: Biology and impacts of Pacific Island Invasive Species.  Pacific Science 61:1.

  • Memberships & Affiliations

    • A Rocha Canada—Christians in Conservation (founding board member, served from 1996-2011)  

    • Agricultural Institute of Canada – member of Scientific Journals Committee (2008-2010)

    • American Scientific Affiliation/ Canadian Christian and Scientific Affiliation (member)

    • Canadian Journal of Plant Science, Associate Editor with responsibility for the Biology of Canadian Weeds Series (2004-2009)

    • Canadian Weed Science Society (President; chair of Biology of Weeds committee + served 4 years with the Awards committee)

    • Derek Double Day Arboretum stakeholders group (2008-2012)

    • Garry Oak Ecosystems Recovery Team

    • Invasive Plant Council of BC (member of research and development committee)

    • Journal of Crop Improvement (editorial board 2001-2010)

    • Langley Environmental Partners Society (board of directors 2001-2009; Chair 2008-2009)

    • Langley Field Naturalists board member (2010-2011)

    • The Northwest Scientific Association

    • Pacific Science Board of Editors (2007-present)

    • Salmon River Enhancement Society (board of directors 1997-2010)

    • Soil and Water Conservation Society (Treasurer for the BC chapter 2004-present)

    • University of British Columbia (Faculty Associate in the Forest Science Department)

    • Weed Research editorial board (2007-present)

    • Weed Science Society of America 

  • Courses Taught at TWU

    Principles of Biology (BIOL 113)
    Introduction to Biology I, Ecology and Biodiversity (BIOL 103)
    Biology of Vascular Plants (BIOL 212/312)
    Biology of Nonvascular Plants (BIOL 214/314)
    General Ecology (BIOL 381)
    Plant Ecology (BIOL 316)
    Tropical Botany (BIOL 318)
    Biology and Christian Theology (BIOL 390)
    Developing a Christian Worldview in the Natural and Applied Sciences (NATS 487, 490)
    Senior Thesis Supervision (BIOL/ENVS 409/410)

  • Awards & Honours

    LEPS Stewardship Volunteer of the Year Award Recipient 2009

  • Area of Research

    My research focuses on the biology and ecology of invasive plants.

    I have investigated invasive plants within a variety of threatened environments such as Garry oak ecosystems in the BC Gulf Islands, arid grasslands of the southern Okanogan valley, and riparian areas of coastal BC. I am interested in developing a better understanding of invasive species that threaten these areas, looking at seed banks, ecotypic variation, response to herbivory and potential for allelopathy. Some of this research is facilitated by access to a 70-acre property on Salt Spring Island, known as the Trinity Western University Crow’s Nest Ecological Research Area which includes several Garry oak meadows.

    Current invasive weed projects include:

    • Biology and control of mile-a-minute weed () in China and the Pacific Islands
    • Canada-wide common garden study on invasiveness of potential biofuel crops (lead by University of Alberta with participants in Saskatchewan, Ontario, Quebec and B.C.)
    • Management of Japanese knotweed (
    • Restoration of Garry oak ecosystems infested by sweet vernal grass (
    • Climate change and weed evolution


      Other research current research projects:

    • Management of invasive fish (largemouth bass and pumpkinseed sunfish)
    • Bioinventory of McLellan Forest in Langley, BC




















    I am on the supervisory committee for two University of British Columbia graduate students studying the impact of red/far red light ratios on plant growth.

    I also conduct extensive literature research on a variety of weed species, contributing to the Biology of Canadian weeds and the Biology of Invasive Alien Plants in Canada series in the Canadian Journal of Plant Science. I am currently a subject editor with Weed Research and on the editorial board of Pacific Science.

Faculty of Natural and Applied Sciences

Department or Program:

Biology, and Environmental Studies
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