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Eucalyptus: Freshwater Species of the Week

Photo: Eucalyptus trees growing in South Africa
Eucalyptus trees were imported to South Africa for timber, but they are now considered invasive because they suck up too much water. David Siu, Flickr Creative Commons

 

Although trees perform many valuable ecological services, not every tree is a “good tree.” Some can be downright problematic, especially when they are invasive, crowding out native species and hogging resources like water and growing space.

This is especially true in South Africa, where invasive plants like imported eucalyptus trees cover about 10% (19-million hectares) of the country, and the invaders are spreading — like weeds — at an exponential rate. But forest managers are fighting back.

A recent report points out the multiple benefits of a longstanding invasive species eradication program, established in 1995 to address “what was then perceived to be the single biggest threat to the country’s biological biodiversity and water security, which intensify the effect of fires and floods and increase soil erosion, while also diverting water from more productive uses, and impeding industries, such as agriculture, fisheries, transport, recreation and water supply, causing billions of rands of damage to South Africa’s economy every year.”

The country’s eradication program has cleared more than two million hectares of invasive plants, while providing jobs for more than 25,000 people a year, many of them hailing from marginalized parts of society, and 54% of them women.

The South African government now spends well over a billion dollars a year dealing with invasive plants, but the recent report suggests that’s not nearly enough.

Christo Marais, natural resource management programs head of operations for the Department of Water Affairs’ Working for Water program, told Engineering News, “The estimated costs of controlling invasive plants, restoring degraded land, implementing an integrated veld and forest fire management program and restoring and maintaining degraded wetlands and riparian zones are orders of magnitude (about R57-billion) more than what government is currently investing, and this is a challenge that might hamper growth in industry.”

Scientists estimate that 9,000 plants have been introduced into South Africa, with about 198 currently classified as being invasive. Among the most notorious are several species of eucalyptus trees, especially E. camaldulensisE. cladocalyxE. diversicolorE. grandis, and E. lehmannii.

Eucalyptus trees are mostly native to Australia and neighboring islands, though they have been imported to many parts of the world for use as timber and as ornamental plants. In many places they have become invasive, since they grow rapidly and often suck up large amounts of water, harming freshwater ecosystems.

A 2011 paper in Biological Invasions by Willem de Lange and Brian van Wilgen suggested that the water lost to invasive plants every year was worth R6.5-billion in South Africa. Without government control efforts, that could have been R41.7-billion, said Marais.

South African officials are now investigating ways to turn invasive eucalyptus trees into biofuels. One pilot program at Farleigh is already turning eucalyptus wood into “eco-furniture,” including school desks.

When people plant trees they typically have the best intentions, but sometimes nonnative species can cause more harm to freshwater ecosystems than good. This can lead resource managers to seek creative solutions.

 

Brian Clark Howard is a writer and editor with NationalGeographic.com. He was formerly an editor at The Daily Green and E/The Environmental Magazine and has contributed to many publications, including TheAtlantic.com, FastCompany.com, MailOnline.com, PopularMechanics.com, Yahoo!, MSN and elsewhere. His latest book, with Kevin Shea, is Build Your Own Small Wind Power System.

Comments

  1. [...] Eucalyptus.  NatGeo’s got this one.  If we had any up here, I’d show you all how to make salve. [...]

  2. elaine angelski
    March 10, 2012, 11:53 pm

    Does the fact that eucalyptus trees suck large amounts of fresh water and are native to Australia mean that they are the reason Australia is such a dry land?

  3. Anant Joglekar
    Yavatmal India
    March 9, 2012, 7:33 pm

    Clonal varieties of Eucalyptus grown for pulp wood have a root zone spread within 5ft x 5ft x 5ft = 125 cft area so the question of pumping fresh ground water does not arise. Eucalyptus is wrongly blamed for sucking up fresh ground water and reducing DGWL (deep ground water level). On the other hand if properly planted eucalyptus adds to the DGWL and also solves the problem of sewerage water in urban areas.
    Yes, the real problem of eucalyptus is the constant and uncontrolled growth or increase in the area under plantations. In many countries old thick forest land is converted in to eucalyptus plantations for commercial purpose of PROFIT in terms of money but of-course ignoring LOSS i terms of environment / nature / bio diversity.