The rapid spread of sickle bush is causing habitat loss and human-wildlife conflict in East Africa.

Experts don’t yet know why this native plant is spreading, but animals from elephants to gazelles dislike it and seek food in farms like those neighboring Randilen Wildlife Management Area in Tanzania.

Methods ranging from burning to chemicals have been suggested to deal with the issue.

Until the bush’s spread is slowed, crude methods ranging from flashlights to fireworks will continue to be employed to keep wildlife clear of crops.

ARUSHA, Tanzania — At the Randilen Wildlife Management Area (WMA) in northern Tanzania, the searing heat and parched terrain make it an attractive hour for a cold swim. A herd of some dozen elephants are doing just that inside a bowl-shaped pool.

For about an hour, a group of visiting scientists remains glued to the spectacle, before the biggest of the pachyderms – which appears to be the matriarch – announces that it’s time to move on, with a snort from her raised trunk.

The scientists agree among themselves that the herd will be moving to fresh grazing grounds for dinner. But that day-end meal could result in confrontation with farmers, says Maglan Loth, one of the rangers at the WMA representing the community.

“When farmers chase away elephants from their farms, [the elephants] keep on returning. I fear this conflict is not only going to continue, but it could worsen,” says Loth.

His fears are understandable. Human-wildlife conflict has intensified due to declining pasture and habitat loss. Elephants from Tarangire National Park bordering Randilen to the east are invading neighboring farms for food at the same time as lions attack and kill livestock that stray into their territory.

“More than seventy percent of crop damages in farms bordering Randilen WMA are caused by elephants. At the neighboring Manyara ranch there is a big problem [of] retaliation when the cats kill livestock,” observes Samwel Shaba, program manager of the conservation charity, Honeyguide Tanzania.

Yet there is no formal compensation from the government for communities when they experience wildlife attacks. Charities like his can only provide a vehicle to take victims to hospital or to facilitate funeral arrangements, he says.

Conservationists are linking the intensified conflicts to habitat loss due to the spread of invasive weeds. Dichrostachys cinerea, or what locals call sickle bush, is an especially choking species which can colonize entire grazing fields, says Meshure Melembuk, the manager at Randilen WMA.

The Center for Agriculture and Biosciences (CABI) lists the weed as native to East Africa, where its ability to produce about 130 shoots from the mother trunk within a 15 meter radius makes it particularly good at spreading and outcompeting other plants preferred by grazers.

“Right now the weed is a very serious problem as you can see. It is replacing grazing land with dense bushes that [restrict] the movement of both livestock and wildlife,” says Melembuk, sweeping his hand in a wide arc over the hills and sunset above Randilen.

Its spread among conservation areas in Tanzania, and East Africa generally, worries experts. Apart from making grazing land shrink, it also disrupts wildlife migration corridors, fueling tension between herders and game, argues Melembuk.

Its prickly thorns irritate grazers like antelopes, while bigger game like elephants do not like its smell. On the other hand, herders do not like venturing into areas that have been colonized by the weed for fear that it could poison their livestock.

“When elephants avoid areas choked by the weed, they move into farms to feed. Smaller animals like gazelles follow. And so will big cats like lions,” says Melembuk, adding that herders also avoid the weed and move their animals to graze in wildlife habitats.

Evidence that loss of biodiversity can fuel human-wildlife conflict was detailed in a new report by UN Environment. As landscapes become more fragmented, wildlife has less freedom to roam, and the report notes that many species are moving less than half the distance they once did.

This limited ability to migrate, disperse, mate, feed and thrive means that wild animals are backed into situations where the threat of extinction looms large, argues the report.

The spread of sickle bush

CABI states that Dichrostachys cineria spreads due to overgrazing. But Mark Sutton, an environmental physicist at the Centre for Ecology and Hydrology argues that invasive weeds can spread fast in situations of high nitrogen and phosphorous.

It is not yet clear whether sickle bush thrives because of this nutrient surge, so it is a subject of study at Randilen WMA. Working with University of York and Ujamaa Community Resource Team, Melembuk and the experts are trying to answer this question.

Once this is answered, Melembuk says, the next step is to try several methods for helping communities to manage the weed. One approach is to overgraze areas colonized by it, the second is burning it, while the third is digging and uprooting it manually. Spraying with chemicals has also been tried in some areas, he says.

“At the end of the research we will compare which method is working effectively. This will be passed on to livestock keepers so that they can use it to eradicate the weed within their grazing lands,” says Melembuk.

Melembuk’s efforts seem as ambitious as they are promising. But his WMA, like many others in Tanzania, are faced with a persistent problem: money. For instance, since its establishment in 2014, his WMA has made an estimated 1.3 billion shillings (about $554,000) from tourism. The government receives 30 percent of this amount, while the WMA receives 70 percent. Further, the 70 percent the WMA receives is split into two, where half goes to the community and the other half is retained to fund operations of the WMA.

“Most of this money is used for social development like building schools and dispensaries, leaving nothing to manage emerging conservation threats like invasive weeds,” Melembuk states.

However, Tanzania’s minister for water and irrigation, Makame Mbarawa, when asked for comment at the UN Environment Assembly (UNEA) meeting in Nairobi this week, defends the government’s arrangement, arguing that cost sharing is part of the country’s wildlife policy, and that it prevents the mushrooming of WMAs.

But WMAs still must overcome the cash crunch. This is why charities like Honeyguide Tanzania are proposing establishment of a conservation fund within WMAs as a way of making them more independent.

Others like the Kenya Wildlife Conservancies Association (KWCA), composed of 12 regional associations and a network of conservancies, propose removal of revenue sharing between WMAs and the government, while allowing WMAs to establish alliances among themselves, as is the case in Kenya, according to Dikson Kaelo, the association’s chief executive officer.

Conservancies there generate revenue and retain it in order to safeguard wildlife, secure the land, and provide services, all of which are government functions, Kaelo says.

“The Tanzania government needs to support WMAs first of all by making sure they retain all the money they generate. Secondly, the government should invest in WMAs because it is in the government’s interest that these areas are well kept so that wildlife can be connected and can continue moving,” argues Kaelo.

Such a prospect might seem ambitious but not impossible, according to Joyce Msuya, the acting executive director for UN Environment, and a Tanzanian national herself who is also at the UNEA event this week.

In her capacity at the UN, she is keen on working with the Tanzanian government to empower WMAs to deal with the twin threats of invasive weeds and human-wildlife conflict.

This is because Tanzania’s economy depends a lot on tourism and the biodiversity industry, she says, adding that the immediate action that effected communities can take is to address the problem of invasive weeds, before it worsens.

“My advice to farmers and communities affected by the weed is to raise the issue with the government so that we can team up and help them deal with the problem. This is because spread of invasive weeds does not respect political or geographic boundaries,” Msuya suggested.

However, there’s another solution that the government of Tanzania is pursuing, Minister Mbarawa says, the establishment of wildlife corridors to prevent conflict with communities living on the flanks of conservation areas.

Kipkorir Koskei, the senior technical advisor at the African Risk Capacity, an agency of the African Union, argues that proper land use management would be a smart way to prevent habitat encroachment by invasive weeds in East Africa.

The UN report proposes the use of tools including genetically engineered organisms as means of eliminating invasive species, including choking weeds, but according to Christopher Cox of UN Environment’s ecosystem division, in some cases, depending on a particular organism and intensity of encroachment by the invasive weed, biological control also could work. This would involve the use of insects that consume certain essential parts of the plant when it is reproducing, or in its early stages of growth, says Cox.

However, biological control itself must not be allowed to get out of control and ruin other things in the ecosystem, he cautions. “Introducing genetically modified organisms or even biological control to battle invasive species has to be done with a very good scientific understanding and also very good understanding of the social implications,” says Cox.

Cruder crop protection tools still used

Meanwhile, steps are taken to ameliorate the human-wildlife problem with simpler tools, as demonstrated inside the Randilen WMA one morning.

A ‘grenade’ made from a condom stuffed with chili powder and fitted with a fuse sunders the morning calm at the rangers post, and is received with a cheer by a group of visiting scientists, as others search for traces of the explosive’s debris on the ground.

There is none, and that is what makes it a useful method for scaring stray elephants away from the conservancy’s neighboring farms, suggests Shaba of Honeyguide Tanzania.

With a 70 percent success rate, this is one of several simple technologies that charities like his are transferring to communities to scare game away instead of killing them.

Other tools in the crop protection program include a flashlight which is 70 percent effective, a blow horn rated at 35 percent, and fireworks like Roman candles, which Shaba maintains are 99 percent effective at chasing animals off crops.

“We get village representatives, train them to be village crop protection teams, then they can go and train others in the community. It is up to them to decide how to get out at night to protect their farms from raiding elephants,” says Shaba.

Until the spread of habitat-choking sickle bush is slowed, wildlife will continue seeking food on farms, and tools like these will remain in use.

Editor’s note: the original version of this story misidentified Patrick David, Randilen WMA’s field operations officer, in image captions, and that has been corrected.