The Brazilian countryside, at least in the central southern region where I lived, is beautiful. The city of Uberlandia is situation in savanna, and as you go east toward Belo Horizonte it's more prone to forests. There is agriculture everywhere, of course, but as in the United States the natural features of the various regions are still in evidence. It was in my infrequent trips between cities there that I saw eucalyptus plantations and thought them to be majestic. It turns out that there is a great deal of debate about them.
Native to Australia but now found worldwide, eucalyptus refers to a large genus of over 800 species of shrubs and tall trees. Often the ones cultivated are hybrids of two or more of these.
What these trees have against them biologically is that they are allelopathic consumers of large amounts of water and nutrients that spread by seed. To many these are an invasive species, while to others they're very useful for producing a large amount of lumber in a relatively short period of time. There is also scientific debate about whether they really deplete subsoil moisture significantly, and regarding how long it takes for the water levels to return to normal once they are harvested.
In the bigger picture of environmental impact they are often a replacement for older forests or jungles that represent a great deal of diversity lost. As a monoculture, what they offer to wildlife is considerably more limited than natural woodlands. What often happens in Brazil is that rainforest is cleared and put to use for traditional crops or cattle, and when the soil is depleted the eucalyptus trees come in. It seems likely that in the future most of what is now rainforest in Brazil will be soybeans, cattle, and eucalyptus. Great perhaps for our supply chain, but terrible for the natural world.
Research has recently come forth showing that a genetically-modified variety of eucalyptus that does not produce seeds is possible, removing at least in theory concerns over it spreading outside of cultivated areas.
Oregon State University’s Steve Strauss led an international collaboration that showed the CRISPR Cas9 gene editing technique could be used with nearly 100% efficiency to knock out LEAFY, the master gene behind flower formation.
“The flowers never developed to the point where ovules, pollen or fertile seeds were observed,” Strauss said. “And there was no detectable negative effect on tree growth or form. A field study should be the next step to take a more careful look at stability of the vegetative and floral sterility traits, but with physical gene mutation we expect high reliability over the life of the trees.”
Findings were published in Plant Biotechnology Journal.
Strauss, Ph.D. student Estefania Elorriaga and research assistant Cathleen Ma teamed up with scientists at the University of Colorado, Beijing Forestry University and the University of Pretoria on the research. The greenhouse study involved a hybrid of two species, Eucalyptus grandis and E. urophylla, that is widely planted in the Southern Hemisphere; there are more than 700 species of eucalyptus, most of them native to Australia.
“Roughly 7% of the world’s forests are plantations, and 25% of that plantation area contains nonnative species and hybrids,” said Elorriaga, now a postdoctoral researcher at North Carolina State. “Eucalyptus is one of the most widely planted genera of forest trees, particularly the 5.7 million hectares of eucalyptus in Brazil, the 4.5 million hectares in China and 3.9 million hectares in India.”
Those plantings, the scientists note, can lead to undesirable mingling with native ecosystems. Thus eliminating those trees’ ability to sexually reproduce without affecting other characteristics would be an effective way to greatly reduce the potential for invasive spreading in areas where that is considered an important ecological or economic problem. (via Oregon State University)
This isn't a solution that will be widely-accepted, given restrictions on genetically-modified organisms in places like Brazil. It does show us a way forward, I think, in handling the other alleged negatives of eucalyptus trees. If gene modification can produce a variety that doesn't spread via seeds, then perhaps it's also possible to moderate their impact on the environment in other ways, such as water consumption and suppression of other plant life.
Since it's highly doubtful that something as profitable as eucalyptus is going away, the better path is to make it less harmful.