South Africa Is Fighting Back Against Invasive Plants

Every spring, Johannesburg’s streets are transformed by a sea of purple as thousands of jacaranda trees burst into bloom. The lavender canopy is a defining feature of the city, as well as of nearby Pretoria.  

But few know this iconic tree is actually an intruder.  

Originally from South America, jacarandas are one of hundreds of invasive species reshaping South Africa’s ecosystems. Together, these invasives deplete water supplies, fuel wildfires and crowd out native plants. They cover about 10% of South Africa’s land, an area larger than Iceland.

Globally, invasive species cost the economy more than $423 billion each year. They also threaten agricultural productivity, biodiversity, infrastructure and human health. Climate change is only making the problem worse. Warmer temperatures and changing rainfall patterns weaken native ecosystems, giving invasives a competitive advantage.

Yet, with coordinated efforts over time, degraded land can be restored and natural systems revitalized. In the past decade, South Africa has cleared hundreds of thousands of hectares of invasive species from its rivers and watersheds. These efforts have replenished vital water supplies for major cities, created new jobs, revived native biodiversity and improved water management.

The Cost of Invasive Species to South Africa

South Africa is one of the most drought-prone countries in the world, receiving just 464 millimeters of rainfall every year — less than half the global average. This scarcity makes the impact of invasive plants on water resources especially severe.

Many invasive plant species consume a lot of water. With aggressive, complex root structures and high transpiration rates, they use between 1.44 billion and 2.44 billion cubic meters of water each year — equivalent to as many as 976,000 Olympic swimming pools. Studies estimate that invasive plants reduce national streamflow by nearly 3% per year, with their impact intensifying during droughts.

Johannesburg, South Africa’s largest city and economic hub, draws much of its water from the Vaal River and Orange River catchments, where invasive plant infestations threaten its freshwater supply. Invasive species also contribute to major flooding in the city. Dense thickets of South American bugweed and Australian black wattle clog tributaries of the Jukskei and Klip rivers, causing them to overflow during heavy rainfall and flood neighborhoods such as Alexandra.  

Together, these pressures put Johannesburg under mounting water strain.

The Strain on Biodiversity and Agriculture

Invasive plant species also threaten South Africa’s biodiversity. In the Western Cape, for example, clusters of 10-meter-tall black wattle trees displace native fynbos, a type of heath mostly made up of hardy, evergreen and highly diverse shrubs. These types of losses can alter entire ecosystems.

They also pose a growing and costly problem for South African farmers. Non-native plants such as lantana and prickly pear reduce arable land, poison livestock and require expensive chemical or mechanical removal. Some farmers turn to the cheaper alternative of simply burning infested fields — a practice that creates additional environmental risks, including soil degradation and wildfires.

Faced with intertwined environmental, social and economic threats, South Africa has found ways to restore its landscapes and create healthier, more balanced ecosystems.

How South Africa Is Responding

The most immediate way to address invasive species is to remove them. But this approach is often costly, labor-intensive and only effective when paired with long-term management and supportive policies. As a result, South Africa’s strategy combines national programs, regional buy-in and local community action, turning an invasive crisis into an opportunity for resilience.

Protecting Water Sources

To protect its water sources, South Africa has pioneered one of the world’s most ambitious invasive species management programs: Working for Water. Launched in 1995, the program removes invasive plants from catchments, rivers and reservoirs, helping to increase water supplies. It also creates thousands of jobs in landscape restoration, particularly for women and youth, by equipping them with the skills and equipment needed to clear invasives from the environment.

Since its beginning, Working for Water has cleared over a million hectares of invasives across the country in collaboration with provinces and municipalities. In the Western Cape, the program works with the Greater Cape Town Water Fund. Together, they have cleared 46,000 hectares of invasives since 2023, recovering more than 15 billion liters of water each year for Cape Town’s residents — an amount equal to about two weeks’ supply for the drought-prone city of 5 million. 

In the Eastern Cape, Stewards of Nature, in collaboration with WWF South Africa, developed a Water Impact Calculator to quantify the water recovered through invasive species removal. Using this tool, they found that clearing just 269 hectares — an area smaller than New York's Central Park — of invasive black wattle and Port Jackson (a small flowering tree) freed enough water for more than 16,000 households for a year. This approach not only restores water resources but also helps communities adapt to environmental challenges while supporting biodiversity.

Managing Floods

To help Johannesburg better withstand floods, local communities are clearing invasive plants along the city’s riverbanks. This includes initiatives like the SUNCASA project, which focuses on removing fast-growing invasives that clog waterways — a problem that becomes especially serious when the Jukskei River floods.  

Clearing invasives from the Jukskei riverbank also helps restore ecosystem health and opens up riversides for natural infrastructure such as parks and green buffers. These efforts are focused on flood-vulnerable neighborhoods and townships, such as Alexandra, where flooding puts thousands of people at risk every spring.

The Future of South Africa vs. Invasives

South Africa’s experience with invasive species shows how dramatically ecosystems can be reshaped — and how costly inaction can be.

Removing invasives is an important first step, but it’s not a "one-and-done" solution. Landscape management is continuous: after removal, ongoing site management is needed to keep areas invasive-free. This requires coupling removal efforts with durable policy solutions. Local and national governments must invest in coordinated, long-term strategies that combine ecological restoration, job creation, public awareness and cross-border cooperation.

As climate change accelerates, the threat from invasive species grows. Resilience planning must treat invasives as an immediate and expensive threat to ecosystems, water security and climate adaptation efforts.