Remote sensing and Community perception evidences on the Impacts of land use/cover change on natural resources in Rungwe Volcanic Province in Tanzania

In the highlands of southern Tanzania, the land tells a story of two worlds colliding. On one side stands the ancient, steep slopes of the Rungwe Volcanic Province, a region defined by its rich volcanic soil and cool mountain air. On the other lies the vast, warm expanse of Lake Nyasa, a massive body of water that borders Tanzania and Malawi. For centuries, these two landscapes have been linked by a delicate natural system: rain falls on the high mountains, soaking into the earth to feed rivers that flow down to the lake, while the lake itself sends moisture back up to the hills. This cycle supports everything from the forests that cling to the slopes to the farms that feed the local people. However, this balance is fragile. When people clear forests to plant crops or build homes, they change how water moves through the land. This process, known as land-use change, can turn a steady flow of water into a flash flood or a dry riverbed, threatening both the food people grow and the safety of their communities. Understanding how human activity reshapes these landscapes is crucial for anyone living in or visiting such regions, as the decisions made on a hillside today can determine whether a village floods or dries up tomorrow.

A recent study by researchers Benard Mwakisunga and Hance Njobelo brings this story into sharp focus for the Rungwe Volcanic Province, which includes the districts of Rungwe, Busokelo, and Kyela. The team combined two very different ways of seeing the world: they looked at the ground through the eyes of the people living there, and they looked at the same land from space using satellite images taken over thirty years. By comparing what the community remembers with what the satellites show, the researchers built a clear picture of how the landscape has transformed. They found that the area is changing rapidly, driven by a growing population and a shift in what people choose to grow. The population is increasing due to both high birth rates and a steady stream of new residents moving in from neighboring regions and countries. These newcomers are drawn by the promise of farming specific crops, such as avocados and Irish potatoes in the highlands, and rice, cocoa, and palm oil in the lowlands near the lake.

As more people arrive and more land is needed for farming and housing, the natural cover of the region is disappearing. The researchers observed that forests, which were once used for firewood and traditional community needs, are now being cut down to make way for fields and charcoal production. In the highland areas, the dense closed woodlands have shrunk dramatically, replaced by open woodlands and fields of crops. In the lowlands, permanent swamps and grasslands are being converted into agricultural land. This transformation is not just a change in scenery; it is altering the very way water moves through the province. The study reveals a troubling pattern where the rivers flowing down from the mountains are losing water, while the lake at the bottom is receiving too much sediment.

The community members interviewed for the study confirmed these changes with their own observations. In the highlands and midlands, seventy-five percent of the people reported that the water levels in their local rivers are dropping. They attribute this to the removal of trees and the planting of crops right along the riverbanks, which leaves the soil exposed to erosion. When it rains, the loose soil washes away, clogging the riverbeds and reducing the amount of water that can soak into the ground to recharge the underground aquifers. In contrast, people living near the lowlands and the shores of Lake Nyasa report that the lake's water level is rising. This rise is not due to more rain falling directly on the lake, but rather because the rivers are carrying a heavy load of mud and silt from the eroded hills above. This sediment fills the lake, pushing the water level up and causing it to spread onto the land where people live and farm.

The impact on agriculture is mixed and depends on where a farmer is located. In the lowland areas, crop yields are falling. Farmers there blame the decline on poor soil quality, unpredictable rainfall, and long periods of drought. The soil, stripped of its natural nutrients and covered in sediment, is struggling to support the crops. However, in the midland and highland zones, some farmers report that their harvests are actually increasing. This is largely because they have switched to new, high-value crops like cocoa and avocados and are using fertilizers and pesticides to boost production. Yet, this success comes with its own risks. The increased use of chemicals threatens the health of the rivers and the lake, while the shift away from traditional, diverse crops makes the farming system more vulnerable to pests and market changes.

The researchers also noted that the pace of this change is not the same everywhere. The districts of Kyela and Rungwe have experienced the most dramatic shifts in land cover, with forests and wetlands giving way to farms and settlements at a faster rate than in Busokelo. The satellite images, which tracked the land every ten years from 2000 to 2020, show a clear trend: closed woodlands are vanishing, and areas of mixed cultivation and urban development are expanding. This expansion is driven by the need to feed a growing population and the economic pull of cash crops. The study concludes that while the community is adapting to these changes, the current path is unsustainable. The loss of forests and the degradation of riverbanks are causing more frequent flooding in the lowlands and drying out the rivers in the highlands. To protect the future of the region, the authors suggest that the community needs to be more aware of how their land use affects the entire ecosystem. They call for better planning to manage the land and a deeper understanding of how the rivers and lakes respond to the changes happening on the hills above.