The film shows a mass of water with an island full of birds, dense forest covering several hills, a fast-flowing river whose water is brownish, a stretch of denuded land featuring gullies and tree stumps and the birds again.
"There are several major environmental concerns in Burundi, the main one being deforestation, which has led to the depletion of a lot of the country's natural resources," Sabushimike told IRIN in Bujumbura, the capital. "The destruction of natural resources is the beginning of the problem of climate change in the country."
The professor, who has conducted environmental research for more than a decade, is an expert on prevention and management of natural risks and disasters. His documentary was commissioned by the Burundi Nile Basin Discourse (NBD) [www.nilebasindiscourse.org] - an organisation of civil-society groups that deals with environmental matters. It is part of efforts to sensitise the population to the need to conserve and protect the environment.
The destruction of the natural ecosystem of Kibira Forest - the country's largest, for example, has contributed to the adverse effects of climate change in the country, according to Sabushimike.
This had subsequently led to the degradation of agricultural land, because of the intense usage of soil in many areas.
The other major environmental concern was the degradation of marshlands and lakes, due to the adverse climatic conditions experienced in such areas. As a result, drought and desertification have led to a drastic drop in water levels in the lakes and the drying-up of marshlands.
Mining has also contributed to the destruction of the environment, Sabushimike said.
The consequence of all this environmental degradation has been increased poverty, especially among rural communities; food insecurity arising from poor agricultural practices; diminishing waters resources; a reduction in activities in the agricultural, forest, energy and health sectors.
Burundi is one of several African countries to have signed conventions such as the National Plan of Action for Adaptation to Climate Changes and the Framework Convention for National Communication on Climate Change. The first aims to improve seasonal climate forecasts for early warning purposes; rehabilitating degraded agricultural areas; protecting natural ecosystems; capacity-building in the prevention and management of natural disasters due to climate change; and, community sensitisation.
To mark World Environment Day on 5 June, the government has organised weeklong activities. These include rubbish collection and tree-planting in the city as well as in all the provinces, and clean-up exercises in rural and urban areas.
The NBD, the national forum for the regional Nile Basin Initiative (NBI), covering 10 countries that share in the management of resources from the River Nile, is also planning several activities to mark World Environment Day.
"We want to move away from the speeches and the workshops and go directly to the affected populations," Albert Mbonerane, NBI national coordinator and former environment minister, told IRIN.
"We will be in Muramyva Province, mobilising the people in building gabions on the hilly slopes in efforts to stem soil erosion," he said. "By involving the communities in actions like these aimed at curbing soil erosion, we hope to cover the whole country in two years, and hopefully reverse the damage already caused."
For its part, the Nile Transboundary Environmental Action Project (NTEAP), will be in Gitega Province, undertaking similar activities aimed at protecting and conserving the environment. NTEAP is a project under the NBI.
Mbonerane said although Lake Tanganyika, the biggest water body in the country on whose shores the capital is built, was not part of the Nile Basin lakes, its wellbeing was of concern to the NBD as the reduction of its water level had an indirect effect on the other smaller lakes in the country that fall under the Nile Basin.
"It is clear that the water level of Lake Tanganyika is decreasing every year," he said.
The reduction in the lake's water level has led to increased evaporation due to adverse climatic changes; the deepening of River Lukuga in the Democratic Republic of Congo (DRC) into which some of the marsh areas feeding the lake had drained their waters; and the non-protection of the hillsides leading to eroded soil filling up the lake.
Water levels had also gone down after a reduction in the amounts of water delivered by rivers feeding the lake. "Previously, some of these rivers flowed all year into the lake, but some have since become seasonal, thus the amount of water going into the lake is not as regular," Mbonerane said.
Uncontrolled agricultural activities close to the lake's shores had also contributed to the shrinking of the surface of the lake as well as its falling water level.
"Previously, there was a stretch of no-man's land that separated the lake from the rest of the land where human activities could be carried out but no more; now there is cultivation right up to the shores of the lake," he said.
When it rains, all the soil eroded from the surrounding farmlands ends up in the lake, further lowering the level of the lake.
In coming years the issue of a lack of water could cause wars in the region, Mbonerane said. "Can you imagine a day without water? That is why the countries that have a direct bearing on the River Nile got together to undertake national and inter-country projects that we hope will keep us away from fighting over water resources."
Whenever one of the 10 countries - Kenya, Tanzania, Uganda, Rwanda, Burundi, the DRC, Ethiopia, Sudan, Egypt and Eritrea (which has observer status) - implements a water project that affects the Nile, an impact analysis is made and each country consulted.
An example was the Kagera project, which involves using water resources from River Kagera in Tanzania. Burundi, Rwanda and Tanzania are involved in the project since they share the resources of the river.
In Burundi, five lakes - Cohoha, Rweru, Rwihinda, Kanzigire and Gacamirinda - fall under the Nile Basin, most of them in the northern province of Kirundo. "All these lakes have a big problem," Mbonerane said. "In the past 10 years or so, the region has experienced drought and increasing desertification, leading the population to resort to cultivating very near the lakes to get water. The consequence has been a sharp reduction of the lakes' surfaces."
Lake Cohoha featured in Sabushimike's documentary film; it is the largest of the lakes and most threatened by climate change.
"These lakes don't have rivers feeding them; instead their waters are from underground springs," Mbonerane said. "Evaporation and cultivation around these lakes have endangered the region's biodiversity. In fact, in Lake Cohoha, the destruction has meant a major reduction of the birds that initially inhabited the various islands in the lake."
Sensitisation of the population in environmental conservation and the need for sustainable development is the only option if the effects of climate change are to be reversed in Burundi, Mbonerane said.
"On the national level, sensitisation of the people is the main thing right now," he added. "This will help us achieve sustainable socio-economic development."