How Ipomoea Took Over Up to 65% of Pastureland in Parts of Kajiado

When people talk about Ipomoea in Kajiado, the conversation often starts with one number: 65%.

That figure has appeared in meetings, community discussions and conversations among pastoralists for years. But where does it actually come from? Does it describe the whole county? And what does it really tell us about the state of Kajiado's rangelands?

The answers are more nuanced and more revealing than the headline statistic alone.

Check out Article 1; Anchor: our overview of Ipomoea in Kajiado

Where did the 65% figure come from?

The number comes from one of the most comprehensive published studies on Ipomoea invasion in Kajiado County.

In 2015, researchers from KALRO's Arid and Range Lands Research Institute worked with pastoralists, farmers, government officers and community representatives to understand how extensively the weed had spread. Rather than relying on a single source of information, they combined field visits, interviews and focus group discussions to build a picture of the invasion across the county's worst-affected areas.

The results showed remarkable agreement.

Community members estimated that Ipomoea covered about 65% of pastureland in Kajiado Central and 50% in Mashuru. Researchers' own field observations suggested that some heavily invaded localities had already reached 60–80% pasture cover.

Those figures remain the most detailed published estimates available today.

It isn't the whole county

One important detail is often overlooked.

The study was never intended to estimate county-wide invasion.

Instead, researchers deliberately focused on four locations that government agencies and local stakeholders had already identified as among the most heavily affected:

●      Olbelbel

●      Sajiloni

●      Mashuru

●      Nkatu

That means the findings tell us not only something important, but also something specific.

They show how severe the invasion had already become in Kajiado's hardest-hit rangelands. They do not mean that Ipomoea covers 65% of every grazing area across the county.

Understanding that distinction matters allows us to appreciate the seriousness of the problem without overstating what the evidence actually says.

Why these places?

Across the study sites, researchers consistently found Ipomoea thriving under similar environmental conditions.

The plant was most commonly associated with:

●      flat or gently sloping land

●      predominantly red soils

●      degraded grazing areas

●      landscapes experiencing heavy grazing pressure.

These conditions tell an important story.

Ipomoea isn't simply spreading because it produces large numbers of seeds. It is finding opportunities where the landscape has already been weakened.

Healthy grasslands are surprisingly resilient. But once native grasses are lost through repeated grazing or prolonged environmental stress, invasive plants gain the advantage.

Check out Article 3; Anchor: why degraded rangelands are more vulnerable

Why pasture, and not cropland?

Another finding from the study receives far less attention.

While pasture invasion reached between 50% and 80% in some locations, researchers estimated that only around 10% of cropland was affected.

That difference isn't because Ipomoea avoids farms.

Instead, relatively little crop farming takes place in these parts of Kajiado. Livestock production remains the dominant land use, making grazing land the primary landscape available for invasion.

In other words, the weed is spreading where it has the greatest opportunity—and where the consequences are potentially most significant.

More than just a number

Statistics can sometimes make environmental problems feel abstract.

But imagine standing in a grazing field where two out of every three patches of usable pasture have been replaced by vegetation that livestock largely avoid.

That is what the 65% figure represents.

For pastoral households, it means less productive grazing land, greater pressure on the pasture that remains, and increasingly difficult decisions during dry seasons.

The statistic is important not because it is dramatic, but because it captures how quickly an ecological shift can begin changing the way rangelands function.

A baseline

The 2015 study remains the strongest published evidence we have for understanding the extent of Ipomoea invasion in Kajiado.

It is also now more than a decade old.

Researchers noted that the plant had already been present in the region since at least the 1960s, with community members observing particularly rapid expansion following the 1997–98 El Niño period.

What we don't yet have is an updated county-wide assessment showing how conditions have changed since then.

That gap matters.

Without current data, it becomes difficult to measure whether interventions are working, identify emerging hotspots, or understand how invasion patterns are responding to climate change and changing land use.

Why updated evidence matters

Numbers alone won't restore Kajiado's rangelands.

But good decisions depend on good information.

Knowing where Ipomoea is spreading, how quickly it is expanding and which landscapes remain most vulnerable helps communities, researchers and policymakers decide where restoration efforts should begin and how limited resources can be used most effectively.

At Narresho Alliance, we see updated evidence as the starting point—not the end point—of meaningful action.

In the next article, we'll look beyond the maps and percentages to explore why Ipomoea spreads so successfully in some landscapes but struggles in others, and what that tells us about the health of Kajiado's rangelands.

Check out Article 4; Anchor: why controlling Ipomoea is more difficult than it first appears

References:

Kidake, B. K., et al. (2015). Assessment of the Status of Ipomoea Weed Infestation in Kajiado County, Kenya