LAW BANS CULTIVATION OF LEUCAENA, AN URBAN PEST
A new measure has been introduced in the capital to replace and eliminate city trees considered the world’s most harmful urban weed.
A municipal law in Campo Grande, Mato Grosso do Sul, now prohibits the planting, trade, transportation, and production of Leucaena, an exotic plant that kills native species and threatens surrounding ecosystems.
Violators of the legislation are subject to a fine of R$1,000 (US$177), which doubles in case of repeat offenses.
Leucaena (Leucaena leucocephala) is commonly found in the green areas of Campo Grande and in several other urban regions, including areas near streams.
It is an invasive species known for rapid spread and significant threats to biodiversity.
The plant was introduced to Brazil in the 1970s as an alternative feed for cattle and to recover degraded areas, due to its fast growth. However, its spread became uncontrollable.
Biologists believe the solution lies in managing and monitoring the plant effectively.
According to biologist and researcher José Milton Longo, eradicating the plant completely is a difficult process.
"It forms long-lasting seed banks and regenerates quickly. It is necessary to remove the plant and replace it with a fast-growing native species to prevent it from reestablishing," he explains.
Leucaena often forms dense forests of a single species due to its rapid spread and growth.
The chemicals present in Leucaena prevent other species from growing nearby.
Once its seeds fall to the ground, other plants struggle to sprout or survive in the same space.
The plant releases compounds such as mimosine, which disrupt the growth and development of other organisms and can become toxic to animals over time.
"It dominates the area and causes serious environmental damage. It grows quickly, suppresses other species, and offers nothing for the local wildlife. If consumed in large amounts, it can harm the animals that feed on it," says Longo.
Leucaena kills native trees that provide essential resources for ecosystems, including fruit for birds and pollen for bees.
Gisseli Giraldelli, biologist and regional director of the Brazilian Society for Urban Arborization in the Midwest, explains that when an area is invaded by Leucaena, it begins to lose its biodiversity and can become a so-called green desert. These are areas with very little variety, dominated by toxic species.
"The green desert may look forested, but it consists solely of Leucaena, which poses a threat to both fauna and flora," she says.
Giraldelli also warns that this type of invasion affects human populations.
"The loss of biodiversity in urban environments leads to diseases linked to ecological imbalance. This harms our health and the economy in deeply negative ways."
SEMADES is developing strategies to implement the law and ensure better control and eradication of the plant.
"This is not a quick process. Replacing an invasive species requires careful planning. While science has yet to find a definitive solution for eliminating Leucaena, we focus on control measures," explains Silvia Rahe Pereira, biologist and environmental auditor for SEMADES.
The plan aims to gradually remove and replace Leucaena with native species that protect the local ecosystem and avoid additional harm to biodiversity.