Eucalyptus trees stand tall behind neatly lined tea rows in Sironga, Nyamira County.
By Job Maangi
The lush green hills of the Gusii Highlands have for generations symbolized life, fertility, and abundance. Covering Kisii and Nyamira counties, the region remains one of Kenya’s most productive agricultural zones, blessed with heavy rainfall, rich volcanic soils, and an intricate network of permanent rivers and streams.
But beneath the thriving tea plantations, banana farms, and vegetable fields lies a growing environmental crisis that experts warn could permanently alter the ecological future of the region. The culprit is not drought alone, nor climate change in isolation, but the unchecked spread of blue gum trees near wetlands, springs, and riverbanks.
What was once hailed as a fast-growing “money tree” is increasingly being blamed for drying rivers, shrinking wetlands, disappearing springs, and falling groundwater levels across the Gusii Highlands. Today, environmentalists, local leaders, and courts are converging on one urgent message: if immediate action is not taken to remove eucalyptus trees from riparian zones and water catchment areas, the region risks losing one of its greatest natural treasureswater.
The Gusii Highlands serve as one of western Kenya’s most important water towers. Due to the region’s high altituderising more than 2,100 meters above sea leveland its convectional rainfall patterns, dozens of rivers originate from the hills before flowing westward into Lake Victoria.
Among the most prominent rivers is River Gucha, also known as River Kuja (Gucha), which originates from the Kiabonyoru Highlands in Nyamira County before flowing through Kisii and Migori counties. Another major river is River Sondu, whose waters contribute significantly to hydroelectric power generation through the Sondu Miriu project.
The region is also home to River Mogonga, River Riana, River Eyaka, River Iyabe, River Mogusii, and numerous tributaries that sustain farming, livestock keeping, domestic water supply, and economic activities.
For decades, these rivers remained perennial even during dry seasons. Today, many are under threat.
Residents of Kiabonyoru fetching water from a spring.
Across villages in Manga, Kijauri, Ogembo, Keroka, and West Mugirango, residents are increasingly witnessing a worrying trend. Springs that supplied water for generations are disappearing. Wetlands are shrinking. Streams that once flowed throughout the year are becoming seasonal. In some areas, residents say water levels in sections of River Gucha and River Mogonga have reduced significantly compared to previous decades.
Environmental experts attribute much of this decline to the massive planting of eucalyptus trees around riverbanks and wetlands. Eucalyptus trees were introduced in Kenya primarily for commercial timber production because they grow rapidly and provide quick financial returns. For many families in Kisii and Nyamira, blue gums became an attractive investment due to rising demand for electricity poles, timber, firewood, and construction materials.
However, scientists say the same qualities that make eucalyptus commercially valuable also make it environmentally dangerous when planted near water sources. The trees have extremely high transpiration rates, meaning they absorb and release enormous quantities of water into the atmosphere. Their deep taproots penetrate underground aquifers, while their extensive lateral roots aggressively absorb moisture from surrounding soils. Experts often describe them as “biological pumps.”
A child carries water home.
Dr. Flora Namu, Dean of Natural Resources at Karatina University, warns that the danger is especially severe in wetlands and riparian zones. “Eucalyptus trees are effectively ‘water pumps’ which drain water from underground sources and wetlands. Planting them in water-scarce or riparian areas is essentially a death sentence for those water sources.”
The impact is becoming increasingly visible in the Gusii Highlands, where wetlands once covered by indigenous vegetation are now dominated by dense eucalyptus plantations. Long before the crisis became mainstream, late Nobel Peace Prize laureate Wangari Maathai repeatedly warned about the environmental dangers posed by eucalyptus trees. “Eucalyptus trees have been overpromoted for commercial reasons. They are like a biological pump; they suck up all the water and leave the ground dry. We must protect our biodiversity from commercial greed.” Her concerns are now echoing across the Gusii region as communities witness shrinking rivers and drying springs.
Environmentalists argue that replacing indigenous vegetation with eucalyptus has disrupted the natural ecological balance that protected water catchment areas for generations.
Perhaps the most alarming trend is the widespread planting of blue gums directly within riparian reserves. Riverbanks, valley bottoms, wetlands, and spring catchment areas across Kisii and Nyamira are increasingly lined with eucalyptus trees despite environmental regulations prohibiting such activities. Without vegetation that naturally conserves moisture and stabilizes soils, water infiltration into the ground reduces significantly. During heavy rains, water rushes across exposed surfaces instead of slowly seeping underground to recharge aquifers. At the same time, eucalyptus leaves release allelopathic chemicals into the soil, suppressing the growth of surrounding vegetation and leaving many riverbanks bare. The result is accelerated erosion, reduced groundwater recharge, and declining river volumes.
The environmental crisis carries enormous economic consequences. The Gusii Highlands depend heavily on small-scale agriculture, including tea farming, banana production, dairy farming, maize cultivation, and vegetable farming. As water sources diminish, farmers are struggling with declining crop productivity and increasing water shortages. Crops planted near eucalyptus trees often appear stunted because the trees aggressively compete for soil moisture and nutrients. Women and children are also increasingly forced to walk longer distances in search of water for household use. What is emerging is not merely an environmental concern, but a growing threat to food security and livelihoods.
The growing crisis has now reached Kenya’s legal system. In a landmark ruling delivered in November 2025, the Environment and Land Court issued one of the strongest judicial condemnations of uncontrolled eucalyptus cultivation near wetlands and riverbanks. Justice Oscar Angote ruled: “The unplanned, uncontrolled, and unsupervised cultivation of eucalyptus trees in Kenya amounts to a breach of the right to a clean and healthy environment… These trees shall not be planted, and if already planted, the same shall be uprooted at a distance of less than 30 metres from a wetland or riparian zone.” The ruling is now being viewed as a major legal benchmark in environmental conservation efforts across the country.
Environmental agencies are similarly advocating for the planting of bamboo and indigenous tree species that support water conservation. According to official guidelines from the Kenya Forest Service: “The greatest positive contribution of eucalyptus is perhaps in replacing indigenous species for fuelwood… but generally, planting is not recommended in water-scarce areas, riparian areas, wetlands, and marshy areas.”
Despite growing criticism, the debate around eucalyptus remains complex. For many households in Kisii and Nyamira, blue gums provide one of the few reliable sources of income. The trees mature quickly, require relatively low maintenance, and fetch good market prices.
Bamboo nursery.
Forestry stakeholders argue that Kenya still depends heavily on eucalyptus for electricity poles and construction timber. “Kenya Power will need 1.8 million poles to connect more Kenyans to the national grid. Eucalyptus is arguably the most commercially viable tree because it grows fast and produces straight woodlots. We need the timber, but we need it in the right places,” a source said.
This economic reality means that any conservation strategy must balance environmental protection with community livelihoods. Experts say the solution is not a total ban on eucalyptus trees, but proper regulation of where they are planted. Strict enforcement is needed to prevent planting within riparian zones, wetlands, and water catchment areas. County governments, environmental agencies, and conservation groups must also intensify public education campaigns to help communities understand the long-term dangers of uncontrolled eucalyptus cultivation. Farmers should be supported with subsidized seedlings of bamboo and indigenous trees that conserve water while still providing economic value. Community-led restoration programmes targeting degraded wetlands and riverbanks could also help revive drying springs and rivers.
The battle over blue gum trees in the Gusii Highlands is ultimately a battle for survival. It is about protecting rivers that sustain millions of people downstream. It is about preserving food production in one of Kenya’s most fertile agricultural regions. And it is about ensuring future generations inherit flowing rivers instead of dry valleys.
For decades, the Gusii Highlands have been defined by abundant water, fertile land, and thriving agriculture. But unless urgent action is taken now, the region’s greatest natural blessing could slowly disappear beneath the shadow of the blue gum tree.