GM trees on the march

July 2017

GM trees are coming on in leaps and bounds.  The fruit of the Arctic Apple-tree is making its appearance in American Midwest stores [1], but the big GM tree event is 'short-rotation woody crops'.

Short-rotation woody crops are fast growing trees which can be harvested in just a few years for industrial purposes such as paper and biofuels.  Eucalyptus, which escaped from its native Australia when Captain Cook arrived there, has become one such major crop since the 19th Century.  Because different species are adaptable to many local climates, plantations are now found on every continent.  The next wave, just beginning to gain momentum, is GM eucalyptus.

Woody crops are being touted as environmentally friendly.  This is because, compared to intensive agriculture, they are in the ground long enough to enhance soil quality and carbon storage, reducing soil erosion and nutrient leaching.  Eucalyptus stands allow more rainfall to reach the ground, increasing the amount of soil water by 20-30%.  Non-native crops always affect biodiversity, but whether Eucalyptus leads to good, bad or just different outcomes depends on where its grown, what it's compared with (agricultural crops or native forest), and what biodiversity parameters are actually measured.  If the trees are planted close to the industrial facility which will use them, the inevitable energy cost and pollution from transportation can be minimised.

All this sound very positive, but what's the reality?

Brazil approved GM fast-growing eucalyptus [2] in 2015.  To be profitably productive, eucalyptus needs fertiliser and weed control: this means agri-chemicals, and the faster they grow the more chemicals they'll need.  America is considering an application to grow GM cold-tolerant eucalyptus to widen the geographical range of the woody crop to areas to areas unsuitable for agriculture: GM trees on poor weedy land will mean extra chemicals.  All these chemical needs are exacerbated because eucalyptus doesn't have a dormant period during the year.

Eucalyptus is notoriously thirsty: the increased soil water can easily be offset by the amount that flows back up into the atmosphere through the tree.  If water is already in short supply, eucalyptus will make it worse, and fast-growing GM trees will make it worse still.  If water is plentiful, the Californian experience has shown that eucalyptus can become invasive, and trees are very difficult to kill once they take hold: repeated herbicidal chemical treatments seem to be the only resort.

Wood for biofuel looks set to become another export commodity, elbowing farmers off the land.

Where GM eucalyptus has been added to the landscape, honey exports may collapse.

The Californian experience has also been that forest fires involving eucalyptus are ferocious.  The high oil content of the trees fuels the intensity of the fire and makes them explosive.  Outside their native microbial ecosystem, the dry bark shed from eucalyptus doesn't decompose but accumulates in the area around their base where it provides a large reservoir of dry tinder.

It has been pointed out that all the environmental problems inherent in eucalyptus woody cropping can be made negligible by good management, for example, by growing the stands in a mosaic rather than a monoculture.

However, these involve trade-offs in the wood production that may not be economically feasible. 

The 'green' credentials of eucalyptus appear limited.


Eucalyptus is already raising multiple environmental, agricultural and social concerns.  Fast-growing GM trees and the spread of GM trees in areas previously unsuitable can only make things worse.

If you want to keep up with the GM tree issue and take action, check out and


  • Brazil approves GM eucalyptus trees and 2,4-D-tolerant soy and corn, GM Watch, 9.04.15
  • GM tree for Adverse Temperature,
  • Eric D. Vance, et al., 2014, Scientific Basis for Sustainable Management of Eucalyptus and Populous and Short-Rotation Woody Crops in the U.S., Forests 5
  • Teisha Rowland, How the Eucalyptus Came to California - A Cautionary Tale, Santa Barbara Independent 15.01.11
  • Liza Gross, Eucalyptus: California Icon, Fire Hazard and Invasive Species, KQED Science 12.06.13
Photo: Creative Commons

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