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Alien plants are infecting the Serengeti: A call for action

It was a fascinating few days as many important papers were delivered. One of the very important papers was delivered by Bukombe John Kija. It was more than a presentation; he came to the conference with a call for action. It’s a call to stakeholders – that means all of us.

The paper was titled “Invasion of Alien Plants in Serengeti: A call for management action. After the conference I had a chance to talk to Bukombe. He told me that he was reporting on research he conducted as an employee of the Tanzania Wildlife Research Institute (TAWIRI).

His daily job includes long term research with the Serengeti Biodiversity Program. His current activities include investigating habitat use patterns by ungulates in Serengeti. While doing this work he noticed new plants species. He explained, “Tanzanian alien invasive plants are not well known, though some have been listed by COSTECH. Thanks to COSTECH, for initiating a database of Alien Invasive Plants.

I got exposed to the potential impact of alien species through TAWIRI, I attended a training workshop sponsored by the Grumeti GR and other two conferences organized by the IOBC in Nairobi, Kenya on exotic species in 2010.” Since alien invasive plants can be viewed as the greatest threat to native biodiversity in the world, Bukombe decided to do a systematic survey of alien plants. Previous research has shown that often invasive species enter vulnerable areas such as alongside roads; the process of road construction itself opens the area by disturbing the ecosystem creating a situation which favors foreign invaders.

Others enter through unprocessed food importation as or ornamental plants. Therefore he designed six transects along the main roads in the Serengeti. He checked for plants for three meters from the edge of each side. Strips of road were divided into 500 meter sections. He and his team checked 782 sections; that is 391kilometers on both sides of the road. A solid effort.

Eleven alien plant species were found along the road transects: Amaranthushybridus,T egetesminuta, Daturastramonium, Xanthium strumarium, Cassia occidentalis, Bidenspilosa, Ricinuscomunis, Lantana camara, Sennadidymobotrya, Gomphocarpuskaesneri, and Argemonemexicana. However each species has its own mode of growth and propagation. And two species were seen that were not found along the road transects.

They were Pistiastratiotes (Water cabbage/lettuce) which grows on top of the water and Opuntia vulgaris (Prickly Pear) which prefers offroad sites such as woodland. For the Pistia he sampled locations by using GPS. For O. vulgaris he sampled 50 sites each of which wasa square of 100 meters by 100 meter sequaling 45.2 sq. kilometers. From that they measured the percentage of the area that was covered with O. vulgaris. 11.4% of the area was covered with Prickly Pear. Mammals can’t eat it, they can’t even pass through it.

It makes impenetrable barriers and the native plant species are crowded out. The seeds and plants are coming from outside the Park. Where do they come from? Bukombe Kija said “We do not know for sure because no experiments have been done. It could come through construction when sand and gravel are brought in. Or through tourism and transportation– trucks could be bringing in seeds or plants.

Tourists could be carrying them on their clothing or luggage. Perhaps Lantana is being carried in by birds. And also for example, Serengeti was occupied by people who were using Opuntia as a fence. The people were shifted out of the area, but exotic species of plants that they left in their homesteads were not considered. Opuntia has spread from there.” Bukombe became concerned about the situation of the villages outside the Park but within the Mara River basin.

He went to survey the village areas using transects. The villages include Sirorisimba, Kirumi, Nyamoko, and Kiagata. His list of alien species increased from 13 to 23. The villagers know when each one arrived. They know that Chromolaena grows in the cassava and causes cassava rot. It is so fast growing it out competes the indigenous plants. “We are affected. But it is not yet overwhelming. The invasion is still not much. We can apply physical controls.

It’s possible for most of these species. We need to create awareness and organize control and monitoring groups in all villages. People need to know what is native and what is not native, including their social economic impacts. Not just the common people, but the learned people as well. All stakeholders need to know – which is everybody. We need to prioritize the 23 species. And work on the most crucial ones first. We need to determine their real distributions.

He thinks that the first concerns must be Pathennium and Chromolaena, ” They are growing fast. If we do nothing in 5-10 years they will be uncontrollable. This is the experience other countries have at the moment. They are spreading quickly. We are infected and we need to take action immediately.

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