Abandoned pastures regenerate to low diversity forests without intervention

To start the week, Associate Editor, Cate Macinnis-Ng comments on the recently published article, Abandoned pastures cannot spontaneously recover the attributes of old-growth savannas by Cava et al.

Savanna ecosystems of the seasonally dry tropics cover almost 20% of the earth’s land area. Maintenance of biodiversity in savannas relies on the right amounts of grazing and fire. While overgrazing of savannas is a common threat, a recent paper by Cava et al. shows that simply allowing passive restoration of abandonded pasture sites does not result in a return to an ‘old growth’ savanna in the Brazilian Cerrado.

Using time since abandonment to create a simulation of restoration of pasture through time, the authors found that cover and richness of tree species recovered in about 28 years with minimal intervention. However, the biodiversity of the ground layer did not recover because the understorey was dominated by a small number of non-native grasses and shrubs. Without fire, the regenerating sites resembled forests rather than open woodlands.

As Cava and co-authors point out, restoration goals are key to assessing the effectiveness of passive regeneration. On the plus side, abandoned pastures regenerated to low diversity forest reasonably quickly with no intervention, when fire was suppressed. For restoration of highly biodiverse ecosystems, selective removal of trees and returning fire to the ecosystem may enhance biodiversity by opening habitat and improving light availability.

This research coincides with the recent signing of the Cerrado Manifesto by 40 environmental agencies in Brazil. The document is a call for action on meat and soy production that has been damaging the highly biodiverse savanna ecosystem since agricultural activities shifted away from the Brazilian Amazon in the early 2000s. The manifesto urges companies to commit to policies that reduce deforestation by removing clearance of native vegetation from their supply chains.

Consumer demands for environmentally responsible products and better understanding of restoration options will be a win-win for conservation of Brazil’s unique savannas.

Read the full article: Abandoned pastures cannot spontaneously recover the attributes of old-growth savannas in Journal of Applied Ecology.

5 thoughts on “Abandoned pastures regenerate to low diversity forests without intervention”

Thanks for the 2-in-1 here – not only learning about low-diversity effects in a fire-suppressed, abandoned pasture, but also about the Cerrado Manifesto.

Here on the mid-Atlantic Coast of North America, I would say we have similar effects – tobacco land or pastured land is abandoned, and secondary growth ensues. It would seem that it would take many decades for a similar level of undergrowth (including spring ephemerals) to return to their natural state (if ever). I’m sure if I dug enough, I could find some studies to demonstrate this.

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Interesting. In my experience, abandoned eucalypt plantations may undergo similar regeneration – average to high diversity be attained, but the system probably will not return to the original conditions. But I’ve done only little research on this subject, so don’t put too much trust in my words 🙂
I think much depends on whether underground cerrado structures still exist in the degraded area. If they exist, resprouting greatly aids regeneration. Otherwise, forest species, which rely more heavily on dispersal than on resprouting after disturbances, may come to dominate.

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