Category Archives: Invasive species

Goodbye and watch out for PARTHENIUM!

By Will Knocker:


This is East Gate…notice the Parthenium infested road verges…

KWS you should be ashamed of yourselves: the dreaded Parthenium is taking over Nairobi National Park & what have you done about it?



This innocuous little weed produces tens of thousands of seeds in a matter of weeks & SPREADS.

It is allalopathic (which means it poisons it’s neighbours: other plants) & contains toxic allergins which blister the mouths of grazing animals..


I conducted a workshop a few years ago for FONNAP so ‘Friends’ could recognise & get rid of this horrible invasive weed

KWS did nothing & in fact prevented FONNAP from taking action from doing anything about it..



Parthenium now infests most of Nairobi’s road verges: this is on the Magadi road, ouside Multi Media University…

If you see it (& nowadays most of you will have it IN YOUR GARDENS) , PULL IT UP & LEAVE IT IN SITU.

You have to keep pulling it up over time & attacking it over the long term.


This beautiful white froth means that this rangeland had gone:UNUSABLE forever.

Cattle have been known to die after eating amounts of Parthenium & the allergins get into the milk supply..


If you visit the Athi Basin in the Park & look along the river: you will see great drifts of Parthenium…

A REAL THREAT TO THE PARK & more widely to Kenyan rangelands generally…


This blog is migrating to if you want to continue discussions on Nairobi National Park going into the Future!






Dispersal Area


By Will Knocker:


For many years now, folks concerned with Nairobi National Park & it’s future have discussed the “migration” of wildlife in & out of the Park through “corridors” to a “conservation area” somewhere in the Kitengela. The fact is that NNP is now, to all intents & purposes, surrounded by the city & my purpose in this photo-essay is to show that this is the sad truth…


The only area unfenced along the Southern boundary of the Park is in the Athi Basin, west of Athi River town, where a Block of the Park exists in fact ACROSS the Empakasi river. This Block adjoins an area called the Sheep & Goat land which is supposedly government land but is in fact occupied & grazed by the local Maasai.


Brand new house & fence in this area, supposedly leased by the Wildlife Foundation as open rangeland suitable for wildlife.


This area is vital for the Park’s population of Eastern White-Bearded wildebeest, of which about 250 individuals exist in the Park from an estimated population of 100,000 in the Athi Kapiti ecosystem a hundred years ago…. they give birth to their calves outside the Park.



The area, especially in the woodland within the Park, has been taken over by the dreaded invasive weed Parthenium.


The boundary road along the edge of the Park.


The Athi Plains were rich & very biodiverse, especially in species of large grazers. These are now confined to the Park.


The Last Gnu? We’re nearly there….


A vision of the Future: urbanization & a world in which wild grazers have been replaced by cattle.


The Sheep & Goat Land today (all that is left of the ‘Dispersal Area’): homesteads, roads, ploughed areas, livestock, people, dogs,boda-bodas….is this really suitable for wildlife?


This just about sums it up……


The Park boundary….


This image shows the extraordinary richness of the grasslands of the Athi-Kapiti ecosystem, if it were protected, as this is, by fencing, paradoxically death to the population of wild grazers which once made this area a second Serengeti.

The parcelling out of the plains continues apace: you can buy yours by looking for ‘Kitengela Plots for Sale’ in your paper today.

Luckily, we still have the whole 120 square kilometres of the Park without people, livestock  or fences as a last refuge .




Dreaded Parthenium Threatening Nbi Nat Park

By Will Knocker


Close-up of Parthenium weed, an invasive species rapidly encroaching on Nairobi National Park..this is in the Park, at the Athi dam… I have also seen  invasions along the Athi River -Namanga highway & along the shores of Lake Victoria.

IF YOU SEE THIS PLANT PULL IT UP, (though gloves are advisable for big infestations)


Originally from Central America, this “noxious annual herb appears to have entered the Park in water flows , as well as on the wheels & radiators & under-carriages of vehicles & earth-moving equipment.

Parthenium infestations have CAUSED THE COLLAPSE OF MANY GRASSLAND ECOSYSTEMS AROUND THE WORLD in lands as widely spread as India & Austalia.”

“The FONNAP Natural History Guide to Nairobi National Park”


“No more than half a metre tall, Parthenium releases toxic allelo-chemicals into the soil that inhibit gowth & germination of other species. Its abundant seeds are readily dispersed by the elements.  Each seed can grow within one month into a mature plant capable of producing another 25000 seeds viable for 2 years or longer…


Parthenium contains potent allergins harmful to the health of ungulates & people.”

Contact with this plant causes dermatitis and respiratory malfunction in humans,  in cattle and domestic animals, due to the presence of toxin parthenin.

“Even in mixed forage, the unpalatable leaves,” which blister the mouths of grazers,”taint the flesh & milk of grazing animals. The extent of the potential disruption to the foodchain in incalculable.”


These pictures are taken on the Magadi Road, next to the Media College bumps, but Parthenium is now established (forever…that is the reality of Invasive Species) along all of Nairobi’s new highway & bypass verges. This is within a few yards of the Park…

Thankfully, Parthenium finds it difficult to establish itself in pristine grassland, but alarmingly, it is spreading along the roads & rivers of NNP & especially in the Athi Basi with the new pylon lines. ( No thanks to KWS.)

What can be done?

‘ If the population in cultivated field is light, it should be removed manually. Otherwise it will spread very fast and the population will reach beyond control’… a situation already reached in some parts of the Park.

Last year I organised an Invasive sp. workshop at Silole Sanctuary through FONNAP: it was well attended & we told KWS we were ready to collaborate on removing this dangerous invader from the Park.

The response: nothing.

As far as I am aware there are no efforts being made to eradicate Parthenium, or any other Invasive sp. from the Park…..

More info:

Dreaded Parthenium in NNP

By Will Knocker:


The dreaded Parthenium Weed -spread by human activities such as road building -has gained a foothold in Nairobi National Park, especially in the Athi Basin area, where a pylon line is currently being constructed….floodwater also spreads the seeds, so we can expect mega-infestation after the current Rains…


Each single plant is said to be able to produce 25,ooo seeds -if you want to see the end result, look on the verges of the new by-pass from JKIA heading to the Thika Highway: what a mess….


The experts tell us that this is a plant (it is of the Feverfew family) which poisons its neighbours, including grass & is a major threat to African grassland ecosystems…in Ethiopia (where it first arrived in Famine Relief supplies) it has compromised thousands of acres of rangeland.

Parthenium causes allergic reactions in people & animals, so pull it up with gloves or a handkerchief…..if you see this plant: DESTROY IT!!


Parthenium is not to be confused with one of our commonest & most widely spread wild flower species Heliotropium (see above)

For more information: