India’s open ecosystems face an unusual threat: trees

Sub: Env

Sec: Ecosystem

Context:

A study published in Global Change Biology reported that an increase in tree cover in open ecosystems like savannahs and grasslands has led to a substantial decline in native grassland birds, with the African Savannah experiencing a more than 20% decrease in grassland bird populations.

Woody Encroachment and Its Consequences:

Grasslands and savannahs are biodiverse habitats in tropical and temperate regions throughout the world.
The phenomenon of woody encroachment, where open habitats transition to areas with more tree and shrub cover, leads to a homogenized ecosystem, adversely affecting biodiversity.Grasslands and savannahs, which cover nearly 40% of the earth’s landmass and support various endemic species, are under threat from this change.
Factors such as increased atmospheric CO2, fire suppression, and habitat fragmentation contribute to woody encroachment. This process alters soil conditions and increases predation, particularly affecting specialist species like grassland birds and rodents.
- Increased atmospheric CO2 is likely to promote trees over grasses because the C3 photosynthetic pathway used by trees is favoured under high CO2 conditions.
From megaherbivores like elephants, rhinoceroses, and buffaloes in Africa and Asia to grassland birds like the bustards, floricans, and grouse of the Himalayan grasslands and American prairies, open ecosystems have it all. However, we are rapidly losing them.

Woody Encroachment in India and Beyond:

In India, grasslands face similar threats, with woody encroachment occurring even in protected areas like national parks. Studies have shown significant increases in tree cover and reductions in grassland areas in India and Nepal over the last three decades.
Colonial conservation policies historically classified grasslands as “wastelands,” promoting their conversion into plantations. This mindset continues, with modern perspectives seeing open ecosystems as less valuable compared to forests for carbon sequestration.

Ecological and Conservation Considerations:

The spread of invasive species, often due to tree plantation programs, has exacerbated woody encroachment in grasslands, transforming them into woodlands and further threatening native biodiversity.
Long-term ecological monitoring and research are needed to understand the full impact of woody encroachment on grasslands and to inform conservation policies. There is also a need to reassess and eliminate outdated terminologies like “wastelands” that misclassify and undervalue open ecosystems.

Source: TH