Giant Footprint: How Human Activities Threaten Ecosystem Health
Land Use and Human Impact
Scientists estimate that 80 percent of Earth’s land surface now bears the marks of human activities, from roads and crops to cell phone towers. This widespread land use is having significant implications for the planet’s ecosystems.
Studies show that society is seizing an ever-larger share of the planet’s biological resources to meet human demands. This is raising concerns that the resulting environmental changes may undermine the natural functions of terrestrial ecosystems, threatening their long-term capacity to sustain life on Earth.
Agriculture’s Dominance
Agriculture is the dominant form of human land use today, with about 35 percent of all ice-free land now used to grow crops and raise livestock. This represents a significant increase from just 7 percent in 1700.
The intensity of land use also matters, as more intensive practices consume more resources. Modern farming, for example, has doubled global grain harvests in the last 40 years, but only by expanding cropland by 12 percent. This increased output has been achieved through new grain varieties, chemical fertilizers, mechanization, and irrigation, but it has also led to greater environmental damage, including soil degradation, increased pesticide use, and water pollution.
Biomass Energy Consumption
A recent study compiled spatially explicit maps indicating not only the types of local land use around the world but also the amount of biomass energy—or natural productivity—consumed by various land-use practices. The results showed that humans use up 25 percent of the trophic energy available in all terrestrial ecosystems, despite being just one of millions of species on the planet.
Global Soil Erosion
Another study suggests that the planet’s agricultural land may be more fragile than previously thought. Conventional plow-based farming methods are dramatically accelerating global soil erosion at rates 10 to 100 times above the rates at which new soil is created.
This means that topsoil could be stripped off in as little as a couple hundred to a couple thousand years. While the current rate of erosion may not be immediately apparent, it is a problem that should concern society over the next couple of centuries.
No-Till Agriculture as a Solution
To counter soil erosion, experts advocate for the adoption of no-till agriculture, which forgoes the use of a plow to turn the soil. This approach leaves topsoil less susceptible to erosion and offers other benefits, including improved soil fertility and increased carbon storage.
Soil Erosion and Carbon Levels
For years, scientists have assumed that soil erosion from agriculture plays a role in carbon levels in the atmosphere. However, the exact nature of this link is not well understood. Some studies have concluded that global soil erosion releases considerable amounts of carbon into the atmosphere, while others have found a sizable carbon “sink” effect.
A recent study using a new method of analysis found that global agricultural soil erosion has a minimal effect on atmospheric carbon levels. It does capture carbon, but only a fragment, in amounts well below some previous estimates.
Conclusion
The impact of human activities on terrestrial ecosystems is undeniable. The widespread conversion of land for agriculture, the intensity of land use practices, and the resulting soil erosion are all contributing to environmental changes that threaten the long-term sustainability of life on Earth. Understanding these impacts and implementing sustainable land use practices are crucial for the future of our planet.
