Living Biomass, Carbon Stocks, Carbon-Dioxide Equivalents and Carbon-Trade Potential under Land-Cover Change in Tanzania’s Ruaha-Rungwa Ecosystem, 1995-2050

In the vast, sun-drenched landscapes of eastern and southern Africa, the ground is often covered by a unique mix of trees and shrubs known as miombo. These woodlands are more than just scenery; they are living vaults that store carbon, a gas that, when released into the atmosphere in excess, drives climate change. Scientists measure this stored carbon by looking at the total weight of the living plants, from the tallest tree branches down to the roots hidden in the soil. When forests are cut down or burned to make way for farms or grazing land, that stored carbon is lost, and the vault empties. Understanding how much carbon remains, how fast it is disappearing, and what that loss might be worth is crucial for countries trying to protect their natural resources while also finding ways to fund conservation.

In the heart of south-central Tanzania lies the Ruaha-Rungwa ecosystem, a massive landscape of nearly 4.5 million hectares that includes national parks, game reserves, and the rivers that feed them. This area is a critical home for wildlife and a vital source of water, but it is also a place where the land cover is changing. A recent study by Adili Y. Zella, an economist at the Mwalimu Nyerere Memorial Academy, set out to track exactly how much living plant life and carbon has been lost in this ecosystem over the last three decades and to project what might happen in the future if current trends continue. The research does not rely on complex, high-tech satellite models alone but uses a straightforward method of counting the area of different types of land—such as forest, bushland, and grassland—and applying standard estimates for how much carbon those specific plants hold.

The findings reveal a steady and significant decline in the region's living biomass. In 1995, the ecosystem held an estimated 264.51 million metric tons of living plant matter. By 2025, that figure had dropped to 229.22 million metric tons. This represents a loss of roughly 35.29 million metric tons of plant material over thirty years. Because plants are made of carbon, this loss translates directly into a reduction of 16.59 million metric tons of carbon. When scientists convert that carbon into carbon dioxide equivalents to understand its impact on the atmosphere, the number becomes 60.82 million metric tons. The primary driver of this loss is the shrinking of forests and bushlands, which are being replaced by grasslands and bare soil. While grasslands do hold some plant life, they store far less carbon per acre than the dense woody vegetation they replace.

The study does not stop at looking back; it projects forward to the year 2050 based on a "business as usual" scenario, which assumes that land-use patterns continue exactly as they have in the past without new conservation interventions. Under this projection, the decline continues. By 2050, the living biomass is expected to fall further to 199.81 million metric tons. This means that between 2025 and 2050, the ecosystem could lose an additional 50.68 million metric tons of carbon dioxide equivalents. The researchers emphasize that this is a simulation based on current trends, not a prediction of what must happen, but it serves as a stark warning of the potential future if no changes are made.

Beyond the environmental loss, the paper explores the economic potential of stopping this decline. If conservation efforts could successfully prevent the projected loss of carbon between 2025 and 2050, the avoided emissions could have a significant monetary value in global carbon markets. The study calculates that if the price of a ton of carbon dioxide equivalent were to range from five to fifty dollars, the gross value of avoiding this specific amount of loss could be anywhere from 253 million to 2.53 billion US dollars. At a mid-range price point of twenty-one dollars per ton, the value would be approximately 1.06 billion dollars. However, the author is careful to clarify that these are not guaranteed profits. To actually sell these as carbon credits, the project would need to prove that the conservation is additional to what would have happened anyway, ensure the carbon stays stored permanently, and verify the numbers with rigorous field measurements.

The research highlights that the current numbers are preliminary estimates, similar to a first draft of a financial report, rather than a final audit. They rely on standard averages for how much carbon trees and shrubs hold, rather than specific measurements taken from every square meter of the landscape. To turn these estimates into real, tradeable credits, the next steps would involve planting permanent measurement plots on the ground to count the trees and measure their size, using advanced technology like laser scanning from the air to map the biomass, and measuring the carbon stored in the soil. The study also notes that simply counting the trees is not enough; a complete picture must include the carbon in dead wood, the soil, and the litter on the forest floor, none of which were included in this initial calculation.

Ultimately, the paper paints a clear picture of a landscape under pressure. The Ruaha-Rungwa ecosystem is losing its capacity to store carbon as forests and bushlands give way to open grasslands. While the potential financial value of protecting this carbon is high, the path to realizing that value requires moving from broad estimates to precise, verified data. The study suggests that for Tanzania to meet its environmental goals and potentially access climate finance, it must first establish a solid baseline of what the land looks like today, protect the remaining forests from further conversion, and develop a system that ensures any money generated from carbon credits actually benefits the local communities and the ecosystem itself. The numbers show the scale of the challenge, but the solution lies in the careful, verified work of measuring, protecting, and managing the land with a long-term view.