‘Greenhouse gas emissions from man-managed grasslands similar to global croplands’

As per a new study, emissions of methane (CH4) and nitrous oxide (N2O) from grasslands increased by a factor of 2.5 since 1750 mainly due to increased emissions from livestock.

What are Grasslands?

• Grasslands are the most extensive terrestrial biome on Earth and are critically important for animal forage, biodiversity and ecosystem services.
• They have different names in different regions of the world:
  • In the U.S. Midwest, they are often called prairies
  • In South America, they are known as pampas
  • Central Eurasian grasslands are referred to as steppes
  • African grasslands are savannas
• What they all have in common are grasses, their naturally dominant vegetation.
• They are mainly comprised of grasses belonging to the families Poaceae that include plants like millets, rice, wheat, bluegrass, ryegrass, bamboos, sugarcane and many more. 
• Types: There are two main kinds of grasslands:
  • Tropical: the hot savannas of sub-Saharan Africaand northern Australia.
  • Temperate: Eurasian steppes, North American prairies, and Argentine pampas.

Climate warning from managed grasslands

• Managed grasslands contribute to global warming by the exchange of the greenhouse gases carbon dioxide, nitrous oxide and methane.
• They absorb and release carbon dioxide (CO2) and emit methane (CH4) from grazing livestock and nitrous oxide (N2O) from soils, especially when manure or mineral fertilizers are introduced.
• Direct human management activities are simulated to have caused grasslands to switch from a sink to a source of greenhouse gas, because of increased livestock numbers and accelerated conversion of natural lands to pasture.
• However, climate change drivers contributed a net carbon sink in soil organic matter, mainly from the increased productivity of grasslands due to increased CO2 and nitrogen deposition.

How global croplands contribute to climate change?

• Today, agriculture is a major contributor to challenges facing our environment: land degradation, aquifer depletion, nitrogen runoff and greenhouse gas emissions, etc.
• Agriculture is responsible for about half of global methane emissions. Methane is 26 times stronger as a GHG than CO2.

Methane sources in agriculture

• Ruminant livestock, including cows and sheep, digest their food through enteric fermentation, which produces methane.
• Burning biomass to prepare fields is another methane-maker
• Applying manure to fields.
• Rice grown in paddies, where bacteria break down biomass submerged in the fields.

Suggestive measures

• Sustainable management: These findings highlight the need to use sustainable management to preserve and enhance soil carbon storage in grasslands.
• Reporting: Full greenhouse gas reporting for each country could facilitate the assessment of progress towards the goals of the Paris Agreement and better link national greenhouse gas budgets to the observed growth rates of emissions in the atmosphere.