Pastoralism versus Agriculturalism—How Do Altered Land-Use Forms Affect the Spread of Invasive Plants in the Degraded Mutara Rangelands of North-Eastern Rwanda?

Abstract

Lantana camara L. (Verbenaceae) originates from tropical Central and South America and has become invasive in about 50 countries. It causes problems when invading rangelands due to its toxicity to livestock and its tendency to form dense, monotonous thickets. Its invasiveness can partly be explained by the high tannin content largely protecting the species from being browsed, its tolerance to a wide range of environmental conditions, as well as its general preference for anthropogenically disturbed habitats. The dispersal of L. camara is facilitated by birds and other animals consuming its drupes (endozoochory), and so both wild and domestic ungulates could contribute to its spread. In our study, we investigated the distribution of L. camara in the Mutara rangelands of north-eastern Rwanda, an area that faced dramatic landscape changes in recent decades. We assessed 23 ecological factors and factors related to land-use and conservation-political history. Major effects on the local abundance of L. camara were found in that the relative canopy cover of L. camara was negatively correlated with the occurrence of other shrubs (suggesting competition for space and nutrients), while encounter rates of houses, ‘living fences’ (Euphorbia tirucalli L.) and cattle tracks were positively correlated with L. camara cover. Hence, the spread of non-native L. camara in the Mutara rangelands appears to be linked to landscape alterations arising from the transformation of rangelands supporting traditional pastoralist communities to other agricultural land-use forms.

Biological water quality assessment in the degraded Mutara rangelands, northeastern Rwanda

“…The Mutara grasslands form—together with the Karagwe District in Tanzania and the Ankole grasslands in southwestern Uganda—the Akagera Ecosystem. The original vegetation of the Mutara comprised vast open grasslands and savannah woodlands that are nowadays heavily degraded and predominantly used for cattle grazing (Wronski et al 2015a , 2017 ). Until 1997, large parts of the Mutara grasslands were protected as part of the Akagera National Park and the Mutara Game Reserve (Van de Weghe 1990 ).…”

“…Since the end of the 1990s, Rwanda’s economy has grown dramatically, showing stimulating signs of development (Terrill 2012 ). However, due to still increasing human (483.1 individuals/km 2 ; NISR 2014 ) and livestock densities (64.9 individuals/km 2 ; Wronski et al 2017 ) in areas like the Mutara rangelands in northeastern Rwanda, surface water is increasingly polluted by anthropogenic activities.…”

Water pollution affects fish community structure and alters evolutionary trajectories of invasive guppies (Poecilia reticulata)

“…The area was previously protected by the Akagera National Park and the Mutara Game Reserve, but in 1997 large parts were degazetted and populated by returning refugees and their livestock (Kanyamibwa, 1998). This led to a sharp increase in human population density (483.1 individuals/km 2 ; NISR, 2014) and severe overstocking with cattle (64.9 individuals/km 2 ; Wronski et al, 2017). Further details on the history, ecology and hydrography of our study area can be found in Dusabe et al (2019).…”

A holistic model to assess risk factors of fasciolosis in Ankole cattle

“…The Mutara rangelands comprise vast open grasslands, interspersed by evergreen bushland and thicket (Kindt et al, 2014) and are traditionally used to graze cattle. Today, the Mutara rangelands harbour an estimated 160,000 cattle, resulting in a cattle density of 81 individuals/km 2 (Wronski et al, 2017). Moreover, in a significant part of the Mutara, increasing subsistence agriculture and urbanization, leaving only 13% of the total land area in a natural state (CIRAD, 2002;Wronski et al, 2017).…”

“…Today, the Mutara rangelands harbour an estimated 160,000 cattle, resulting in a cattle density of 81 individuals/km 2 (Wronski et al, 2017). Moreover, in a significant part of the Mutara, increasing subsistence agriculture and urbanization, leaving only 13% of the total land area in a natural state (CIRAD, 2002;Wronski et al, 2017).…”