Savannas of Asia: history, biogeography and management concerns

Jayashree Ratnam, Kyle Tomlinson, Dina Rasquina, Mahesh Sankaran JR, National Center for Biological Sciences, Bangalore, India March 2017@KrugerNP

Photo: Swapna Nelaballi

The classical definition of savannas Mixed tree-grass systems with a discontinuous tree canopy in a continuous grass layer

The classical definition of savannas

Mixed tree-grass systems with a discontinuous tree canopy in a continuous grass layer Within the bounds of this definition, tree cover in world’s savannas is highly variable. Earth’s savannas range from sparsely ‘treed’ grasslands to heavily ‘treed’ woodlands, typically along a gradient of increasing rainfall.

Arid Semi-Arid

Mesic

Increasing Rainfall

Photo credits: http://environment.nationalgeographic.com/environment/photos/savannah; http://www.panoramio.com/photo

“Savannas” range from open arid to closed mesic

Biogeography of tropical Asia- much more mesic

More arid And semi-arid

More mesic

Indian example: Rainfall map

Relative to Africa, where a large part of the savanna regions are arid to semi-arid, a much higher proportion of potential savanna-like regions of India are more mesic .

Formal vegetation classifications of the region established in colonial times By foresters from the perspective of forestry and timber operations All ecosystems with some degree of tree cover are named “Forests” Sankaran and Ratnam, 2013, Ratnam et al 2016

India example: History of vegetation classification

Vegetation Classification of semi-arid and mesic India….

Extracted from Olson’s Ecoregions of the world Olsons Eco-regions of the world- 2012

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Savanna Grasslands - central India (Classification: Dry thorn forest)

Photo: Abi T Vanak

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Savanna Grasslands – western India (Classification: Scrub forest)

Photo credit: Abi T Vanak

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Photo: Abi Vanak

Savanna Grasslands – western India (Classification: Scrub forest)

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Savanna Grasslands – south eastern India (Classification: Dry thorn forest)

Photo: Abi T Vanak

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Scrub Savanna - south eastern India (Classification: Scrub forest)

Photo : Abi T Vanak

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Tree savanna –South eastern India (Classification: Dry Deciduous Forest)

Photo: Swapna Nelaballi

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Tree Savanna –central southern India Classification: Dry Deciduous Forest

Photo: Ed February

Tree Savanna –northern Thailand Classification: Dipterocarp “open forest”

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Photo: Konsant Inroung

Pine Savanna – Phillipines, South-east Asia Classification: Pine forest

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Photo: Kyle Tomlinson

Mapping the potential savanna regions of Asia…..

Africa

Australia

S. America

Where would the savannas of Asia be if the world were like…

Ratnam , Tomlinson, Rasquinha, Sankaran (2016) Phil Trans Roy Soc B

Mapping the potential savanna regions of Asia…..

•African climates provide the closest analogues for Asian Deciduous savannas- both arid and mesic savannas

•Asian pine savannas appear to occur in climates that are distinct from any of the southern continents

•None of the models did a good job of capturing either the savannas of the south east Asian islands

Ratnam , Tomlinson, Rasquinha, Sankaran (2016) Phil Trans Roy Soc B

Management Concerns: Indian savannas

An issue of nomenclature & perception

Grasslands Unproductive, “wastelands” Dry thorn forests, Scrub forests Degraded, “wastelands”

Dry to moist savannas (grassy understories)

Dry deciduous “forests” Moist deciduous “forests”

Grasslands

Arid to semi-arid savannas

Photos: Kalyan Varma

Grasslands, Arid and Semi-Arid Savannas – Most Do Not Have Protection Status, Loss of unique fauna

Grasslands, Arid and Semi-Arid Savannas – No protection; threatened by development activities to make the land more “useful”

Agriculture, water harvesting projects

Afforestation programs that are aggressively being pursued…

Photo: Abi Vanak

Photo: Kalyan Varma

Mesic Savannas– Protection status not a problem But Seen as “forests” and mismanaged

Fires Suppressed Illegal by law Punishable crime Domestic herbivory Often an important Control on the herbaceous layer Actively suppressed

Mismanagement and the invasive species problem

Invasive species (Lantana camara, Parthenium hysterophorus, Chromolaena odorata) are a major problem in the understorey of savanna-grasslands

Different native tribal communities of this area are convinced that the Lantana invasion has come following the imposed suppression of their planned cool season burning of the landscape

Takhekharia, Tamim, Hiremath, Ratnam, Rai, Sukumar, In prep, Notes from the other side of a forest fire; Sundaram et al 2012

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Tree Trait Contrasts: Dry deciduous versus moist evergreen forests confirm a role for fire in DDFs

At this cross-site scale, Savannas (Dry Deciduous forests) show variation in H:D ratios, bark thickness and SLA that are consistent with more lighted, fire-prone environments

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Ratnam et al 2011, Ratnam et al, in prep

Conserving the savannas of Asia

Protection Status needed

Fire management needed

MANY THANKS! THE PEOPLE : Chengappa SK, VijayKumar S, Swapna Nelaballi, Anand MO, Siddarth Machado, Nandita Nataraj, Arockia Catherine & Kartik Teegalapalli ,Dina Rasquinha THE INSTITUTIONS: Forest Department Karnataka, Andhra Pradesh, Tamil Nadu; Scientific Services, Kruger National Park, South Africa; ATREE Field Station @ BRT FUNDING: NCBS (DAE- India), DST, NERC (UK)