Invasive Mesquite Plants Do More Than Deplete Water Reserves New Research In South Africa Shows They Damage Soil Too

(MENAFN- The Conversation) Mesquite (Neltuma juliflora ), a woody plant native to parts of South America, was introduced into South Africa's drylands in the 1880s with good intentions.

Bringing it to South Africa was meant to stabilise soils, provide shade, and offer a source of fuelwood in some of the country's most water-limited landscapes. But today, particularly in the Northern Cape province, it's a clear example of how an introduced species can quietly transform ecosystems, livelihoods and local climates in ways that are difficult and costly to reverse.

Across the Northern Cape's arid and semi-arid rangelands, mesquite has spread extensively along riverbanks, floodplains and grazing areas. Unlike many indigenous plants that lie dormant during dry periods, mesquite remains active year-round. Its deep root system allows it to extract water from far below the surface, steadily depleting soil moisture and groundwater reserves.

I am an environmental and climate scientist in the Northern Cape, where agriculture contributes about 8% of the provincial GDP and employs roughly 16% of the workforce. My work focuses on addressing invasive species, land degradation and climate impacts to protect ecosystems, support rural livelihoods and strengthen the regional economy.

My team and I conducted research into the effect that invasive mesquite has had on the soils in this dry area of South Africa.

We found that mesquite drains moisture and nutrients from the soil, making it hard for other plants to grow. The dense roots and thick canopy also reduce water availability for livestock and people, while the soil becomes compacted and less fertile. All of this together makes farming much more difficult and threatens local livelihoods.

What the science shows

Our study compared soils from mesquite-invaded areas with those from nearby uninvaded rangelands. Our findings show striking differences.

In mesquite-dominated landscapes, soils tended to hold less moisture, had altered nutrient balances and displayed changes in physical structure compared with soils under native vegetation.

This may not sound dramatic at first, but soil moisture and nutrient balance are foundational to how ecosystems function. Soil that stays moist supports grass growth. Grass protects soil from erosion, feeds livestock, and keeps water in the landscape. When mesquite replaces grass with dense thickets, that entire cascade of benefits begins to unravel.

Mesquite roots dig deep and draw water year-round. Where native plants go dormant in dry seasons, mesquite continues to transpire (release water from its leaves), reducing soil moisture. Over time, this leads to drier soils that struggle to support the plants crucial for grazing and wildlife.

The outcome is a quieter, slower form of ecosystem change; one that doesn't always show up in dramatic headlines but that steadily degrades land and undermines livelihoods dependent on healthy soil.

Read more: How South Africa's second most invasive tree can be managed better

Why this matters for climate and livelihoods

Soil and climate are intimately connected. Dryland systems like the Northern Cape are already vulnerable to climate change due to hotter temperatures, more erratic rainfall and longer droughts. In this context, invasive species with high drought tolerance gain an edge. Mesquite, which is native to Central and South America, thrives where native vegetation falters. But that advantage comes at a cost of reduced water availability for human consumption, agricultural use and wildlife, altered carbon cycles and increased land degradation.

For pastoralist communities and smallholder farmers, the effects are tangible. Our team carried out a skills assessment and facilitated workshops in collaboration with the Northern Cape provincial government and the International Union for Conservation of Nature, and documented evidence of these impacts (it is not yet online).

Livestock grazing depends on grass cover. Our direct observations and assessments in the Northern Cape show that as mesquite thickets grow, grazing land shrinks. Farmers find themselves forced to reduce herd sizes or travel longer distances for forage. Over time, income declines, pressure on household food security increases, and people become more vulnerable to climatic and economic shocks.

The human dimension

The invasion of mesquite isn't just an ecological problem; it's a social one. Reduced grazing and degraded land translate into fewer resources for families that depend on livestock. In regions where economic opportunities are already limited, this can exacerbate inequality, increase rural poverty and push people towards unsustainable coping strategies.

Read more: Nearly 25% of land in Africa has been damaged – what's to blame, and what can be done

In our ongoing research, communities across the Northern Cape have told us similar stories: land that used to support healthy herds now supports thorny thickets that livestock avoid; water points dry faster; and the rhythm of life shifts as people adapt to a changed landscape. These are not abstract scientific outcomes; they are lived experiences.

Yet, amid these challenges, there are also opportunities.

Repurposing pathways for mesquite

The same biological traits that make mesquite a problem can also be harnessed for benefit, if approached thoughtfully. Mesquite pods are rich in sugars and have been used as supplementary livestock feed in dry seasons. They could also potentially be used for flour and baking, natural sweeteners, coffee substitutes, snacks, and traditional medicine for regulating blood sugar. The wood is dense and burns hot, making it valuable for charcoal and energy. Craft industries can use mesquite timber for artisanal products, creating potential income streams for rural communities. Mesquite biomass can be processed into low-carbon, climate-adaptive building materials with a net negative carbon footprint, and into biochar that can be used to restore degraded soils after invasive species removal.

The key is to repurpose eradicated mesquite in support of ecological restoration. Overharvesting without a plan can worsen the situation if it encourages regrowth or fails to address underlying ecosystem changes. But when combined with targeted clearing and rehabilitation, utilisation can be part of a broader, sustainable strategy.

Read more: Black wattle as firewood: how South African communities are putting invasive species to work

What needs to happen next

Clearing mesquite is possible, but expensive. Mechanical removal requires labour, machinery and follow-up work to prevent regrowth. If land is cleared but not rehabilitated, grasses and native vegetation may struggle to return because the soil has already changed. That means investment must be long-term, not just a one-off effort.

South Africa needs an integrated approach that includes:

• early detection and mapping

• community-led clearing and rehabilitation, so that efforts are sustained and rooted in local knowledge

• soil restoration efforts, reintroducing native grasses and shrubs

• economic integration, developing value chains for mesquite products

• climate-responsive planning and land management that improves water retention and soil health.

Mesquite invasion in the Northern Cape is more than a botanical curiosity. It is a transformation of land that affects soil, water, climate resilience and human wellbeing. The research on soil properties makes it clear that the impacts are real and measurable, but it also points to pathways for action.

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