Mountain Streams Emits Carbon Dioxide

• 29 Oct 2019

Recently the Scientists have reported the findings of the first large-scale study of the carbon dioxide emissions from mountain streams, and their role in global carbon fluxes.

• Although, mountains cover 25% of the Earth’s surface, but the streams make up just 5% of the global surface area of the fluvial networks.
• This research shows how important it is to include mountain streams in assessments of the global carbon cycle.
  
  • So far, scientists had focused mainly on streams and rivers in low-altitude tropical and boreal regions.
• The scientists collected environmental data from the streams draining the world’s main mountain ranges.
  
  • They specifically focused on their hydrologic and geomorphologic properties as well as the soil organic carbon content within the catchments.
  • They used these data to develop a model to estimate the natural CO₂ emissions from more than 1.8 million mountain streams worldwide.

Findings of the Study

• Researchers found that these streams have a higher average CO₂ emission rate per square meter than streams at lower altitudes, due to the additional turbulence caused as water flows down the mountain slopes.
  
  • They likely account for 10% to 30% of CO₂ emissions from these networks.
• The gas exchange velocities across the air-water interface in mountain streams occurs 100 times faster than previously thought.
• The findings seem to indicate that the CO₂ comes from geological sources, given that carbonate rock dominates geology in numerous regions around the world.
  
  • These rocks were formed from "skeletal" components of marine microorganisms that lived millions of years ago when Earth was largely covered by oceans.

Importance

• It is known for a number of years that freshwater ecosystems emit roughly the same amount of CO₂ that the oceans absorb, but the studies were never done on the role of the mountain streams for the global CO₂ fluxes.
• The latest findings will open up new research avenues, that will help to better understand where all that CO₂ comes from and how a more accurate assessments of the global carbon cycle can be made.
• The findings mark an important step forward but numerous uncertainties still persist.
  
  • It will require long-term monitoring of carbon fluxes in mountain streams to understand how climate change affects their biogeochemistry.

Global Carbon Cycle

• It refers to the exchanges of carbon within and between four major reservoirs: the atmosphere, the oceans, land, and fossil fuels.
• Carbon may be transferred from one reservoir to another in seconds (e.g., the fixation of atmospheric CO₂ into sugar through photosynthesis) or over millennia (e.g., the accumulation of fossil carbon (coal, oil, gas) through deposition of organic matter.

Source: IE