Annonce
Annonce

Arguments and evidence

 

Paulette Vanier and Pierre Lefrançois

 

 What is phytoremediation ?

Formed from Ancient Greek φυτό (phyto), meaning ‘plant’, and Latin remedium, meaning ‘restoring balance’, this word refers to a cost-effective plant-based approach that takes advantage of the ability of plants to concentrate elements and compounds from the environment and to detoxify various compounds. Several field trials confirmed the feasibility of using plants for environmental cleanup1. Willow trees and shrubs are commonly used in phytoremediation. Remediation of contaminated sites or grey waters using willow crops have produced promising results2. Willows’ high evapotranspiration potential allows them to treat large amounts of water3, and they can neutralize even some pesticides found in the soil using three mechanisms : (1) degradation via enzymes and microorganisms found in the rooting zone, (2) plant uptake followed by translocation and metabolism with their tissues, and (3) volatilization via plant transpiration4.

What is a riparian osier-willow buffer strip ?

Osier-willow is used in basketry and wickerwork crafts. It is grown in coppice cultures of willow where the sticks are harvested on an annual basis. Such a crop implemented on a watercourse bank is called a riparian osier-willow buffer strip and it can filter and neutralize pollutants coming from agricultural fields before it reaches the water5. The results of many studies suggest that a 10 meter wide and 1 kilometer long (one hectare) riparian osier-willow buffer strip could catch up, annually, 1.5 metric ton of phosphorous leaching from the fields upstream and that would otherwise pollute the stream and eventually the other watercourses downstream. And it will do so during 15 to 20 years. This is highly significant because we know that phosphate from agricultural fields is the main cause of cyanobacteria blooms, a major environmental problem.

What are Ecosystem Services ?

Per the 2006 Millennium Ecosystem Assessment (MA), ecosystem services are « the benefits people obtain from ecosystems »6. Ecosystem Services are grouped into four broad categories and riparian osier-willow buffer strips provide services in the four categories : provisioning (production of wood fibers, pharmaceutical products), regulating (pollination – willows are very attractive to early spring pollinators – carbon sequestration, water purification), cultural services (recreational experiences, including ecotourism, science and education, art and esthetics) and supporting (nutrient cycles, oxygen production via photosynthesis). Besides protecting watercourses from agricultural phosphate, nitrate and pesticides, the osier plantation can also sequester a good amount of carbon (about 5 tons per hectare – this number needs to be validated later), thus fighting against climatic changes.

Some 65 hectares of osier plantation could solve, within few years, the cyanobacteria problem in Missisquoi Bay and sequester somewhere around 325 tons of carbon yearly.

Meanwhile, we would have also created dozens of jobs and generate more than enough revenues to cover the activities and pursue research on the use of willow for cleaning water, soil and air anywhere in northern hemisphere where willow can be grown.

 

  1. Salt, D.E., Smith, R.D. and Raskin, I. (1998) Phytoremediation. Annual Review of Plant Physiology and Plant Molecular Biology, 49, 643-668.
  2. Ermakov et al. 2015 ; Gomes et al. 2016 ; Guidi Nissim et al. 2015 ; Shi et al. 2016 ; Sylvain et al. 2016 ; Zarubova et al. 2016.
  3. Kuzovkina and Volk 2009 ; Trapp et al. 2001.
  4. Burken 2003 ; Komossa et al. 1995 ; Schnoor et al. 1995 ; Trapp and McFarlane 1995.
  5. Werther Guidi, Frédéric E. Pitre and Michel Labrecque. Short-Rotation Coppice of Willows for the Production of Biomass in Eastern Canada. April 30th 2013. Institut de Recherche en Biologie Végétale (IRBV – Plant Biology Research Institute) – Université de Montréal – The Montreal Botanical Garden, Montréal, Canada.
  6. Johnston R.J. Ecosystem services, https://www.britannica.com/science/ecosystem-services#accordion-article-history