M D Subash Chandran
Centre for Ecological Sciences, Indian Institute of Science, Bangalore:
“Our planet is at a crossroads. The ecosystems that underpin our economy, well-being, and survival are collapsing, species are becoming extinct at an unprecedented rate, and climate change continues unabated” –IUCN expressed its concern for the crumbling environment of our planet. In this context the UN Decade of Ecosystem Restoration 2021 – 2030 can be considered a final call for the mankind to work unitedly for saving our planet from plunging inexorably into an environmental crisis. UN declaration “aims to massively scale up the restoration of degraded and destroyed ecosystems as a proven measure to fight the climate crisis and enhance food security, water supply and biodiversity.” In support states the FAO: “Our global food systems and the livelihoods of many millions of people depend on all of us working together to restore healthy and sustainable ecosystems for today and the future.” Currently, about 20% of the planet’s vegetated surface shows declining trends in productivity with fertility losses linked to erosion, depletion and pollution in all parts of the world. By 2050 degradation and climate change could reduce crop yields by 10% globally and up to 50% in certain regions. Restoration of 350 million hectares of degraded land between now and 2030 could generate USD 9 trillion in ecosystem services while clearing the atmosphere of 13-26 gigatons of greenhouse gases out of the atmosphere.
Our provisions of manifold kinds like food, water, timber, fuel, fibre, medicines, dyes, oils etc. are from ecosystems. Ecosystems perform regulating functions like, purifying the air for breathing, filtering the water for drinking, pollinating flowers to produce fruits; generate soil from rocks, decompose organic matter and integrate into the soil to make it fertile and oxygenated. Healthy vegetation cover prevents soil erosion and flooding by regulating water flow; more safeguarded are humans from landslides in the vicinity of intact natural forests. Carbon storage in biomass has crucial role in climate regulation. On the cultural front ecosystems render priceless services. Patches of primeval forests protected as sacred groves while serving as sources of perennial water, and as gene pools for posterity are still worshipped in villages as abodes of gods. Scenic value ecosystems render runs tourism and recreation; they inspired through time musicians, poets, painters, photographers and film makers. Supporting services from ecosystems, notably are photosynthesis to oxygenate air and water, nutrient cycle etc. are critical to sustain quality life on Earth.
Ecosystem of the Western Ghats
The Western Ghats, predating the Himalayas by 30-40 million years, stretches parallel to the Indian west coast for 1,600 km, covering 160,000 km² area. The Western Ghats-Sri Lanka Global Biodiversity Hotspot, is luxuriant in biodiversity with high degree of endemism. The forests here are rated as the best representatives of non-equatorial tropical evergreen forests anywhere in the planet and are home to at least 325 globally threatened flora, mammal, bird, amphibian, reptile and fish species, as scores remain yet to be evaluated. Considered by UNESCO as a World Heritage Site, the Western Ghats faces threats from rising population, urbanisation and climate change, agricultural expansion, making it one of the eight hottest hotspots of the world. Wildlife corridors are shrinking and get disrupted, and wildlife habitats outside PAs heavily threatened. New roads, broadening of existing ones, and increasing power plants make the situation graver. Invasive species and other habitat impoverishments are driving many endemic fresh water fishes towards extinction. While catchments in the Western Ghats in Kerala, Tamil Nadu and southern Karnataka have the highest freshwater species richness and levels of endemism, they also contain the highest number of threatened species.
How to restore ecosystems of the Western Ghats?
UN visualises ecosystem restoration process “as reducing human pressures on landscapes and seascapes of all kinds and allowing or helping them to recover, boosting their resilience and productivity.” Healthy ecosystems will be essential for achieving the 2030 UN Agenda for Sustainable Development.
Developing concepts towards ecosystem restoration in southern Western Ghats
Restoration of collapsed ecosystems, for eg. in mined areas, landslides, fire burnt stretches, weed infested monoculture tree plantations etc requires serious planning. For those undergoing degradation, reversion to near original may be possible through protection and site specific, time-bound interventions. Forests in degradation stages are departures from ideal systems- our models for restoration. Well preserved sacred groves from ancient times can serve as good, site-specific models for forest restoration, ensuring also endemic biodiversity and strengthening watershed services. Under simple protection itself degraded systems may revert towards original stages through natural re-seeding, depending on the nearness or connectivity with intact systems. Planned interventions using planting of succession-stage specific tree species will hasten the restoration process.
In 1990’s I made efforts towards understanding the forest community structure and dynamics of vegetation change in the high rainfall Western Ghat areas of the 10,200 sq km Uttara Kannada district of Karnataka. From 81 study sites, over 20,000 trees were observed, notably for their species, stem diameter, height classes and regeneration patterns. Forest history of the region was pursued and arrived at the following conclusions (for more details, ‘On the ecological history of Western Ghats, in Curr.Sc. 2007). More studies by our teams followed and the results published over the last two decades. From these various studies the underlying principles of forest structure, functioning and influence on fauna and watershed observed are given below, in the hope that the findings can benefit the restoration ecology in many ways:
- The low to medium altitude climax forests in high rainfall zone (>2000 mm/yr), harbouring high levels of endemism in flora and fauna, are dominated by hygrophilous evergreens like dipterocarps, wild nutmegs (Myristica spp. etc.), Garcinias etc. Although rare such systems are the last refuges for Critically Endangered (CR) Syzygium travancoricum (considered extinct and rediscovered in shaded forests with swampiness), Endangered (EN) Madhuca bourdillonii (feared extinct once to be found later in pristine forest remains), swamp specific Myristica fatua var. magnifica (EN) and Gymnacranthera canarica (Vulnerable -VU). Dipterocarpus indicus (EN) is a dominant tree in swamp and stream rich forests. Semecarpus kathalekanensis, new tree species, close relative of S. travancorica was discovered in an Uttara Kannada forest swamp. Such climax forests or their equivalents persisting through ages are to be preserved as models for directing succession in forests under restoration, to promote forest endemism, paving way for also recolonization by endemic amphibians and stream fishes, among others.
- The intact forests are vertically stratified, so that heavy rainfall reach forest floor as drips and stem flow rather than directly hitting soil. The organic litter covered deep soil absorb water like a sponge releasing surplus as controlled flow through stream networks.
- Most tree species, even the undergrowth produce fleshy fruits in climax evergreen forests. Their seeds are larger, with poor dormancy, being suited more for damp forest floors to germinate early and produce taller saplings that can survive in dim light conditions. Fruits and seeds are mostly animal dispersed. The dipterocarps in general have dry fruits but larger seeds, except in Hopea spp.
- The bark is thin or with medium thickness, softer in texture in climax evergreen species, exuding watery substance or thin latex showing the hydrological richness of clmax forests, which shelter rare epiphytes and wild relatives of ginger, turmeric, pepper etc.
- Most tree are fire sensitive, and die altogether on forest burning. Unlike fire tolerant early successional species these neither coppice nor new shoots spring from roots.
- Growing on mountain slopes in narrow, stream drained valleys, many with buttresses, stilt roots, serpentine roots crawling on wet soil surfaces, these primary forest trees conserve soil and hold on to rock boulders from tumbling down initiating landslides in peak rainy season. Therefore, in Western Ghats forest restoration, climax species components need to be increased.
- Shifting or slash and burn cultivation (by name kumri, hakkal, podu etc.) could have been the earliest agricultural practice in the Western Ghats. The abandoned kumri areas regenerated into secondary forests, which left to itself, would pass through various stages of succession ultimately reaching climax state. Almost all, except few climax tree species, might reappear in the cleared sites in the course of centuries.
- Notable among the species that failed to re-establish on abandoned kumri grounds, even after the stoppage of slash and burn over a century back, primary forest species like D. indicus, M. fatua var. magnifica, G. canarica, M. bourdillonii, S. travancoricum etc. failed to reappear in the secondary sites.
- The early farmers, while clearing forests for cultivation also preserved climax forest patches as sacred groves, especially in prime watershed areas. Such catchment area protection, with taboo on tree cutting in sacred forests, gave us today several precious patches of primary forests having high levels of floral and faunal endemism. Unfailing streams from these groves favoured spice gardens and paddy cultivation in the valleys. The wells and ponds in such valleys never dried up.
- The sacred groves like kans of Karnataka and cardamom forests of southern Kerala yielded several non-timber forest products (NTFP) for subsistence and trade. Wild pepper was taken care of by the village community, probably a practice followed through centuries, as most pepper exported from the west coast ports of Karnataka were the products of kan sacred forests. Such forests also yielded toddy from the palm Caryota urens, which was the source of widely used palm sugar in the region. Cinnamon and cardamom from forests were traded commodities through west coast ports from early historical times.
1. In the early stages of forest restoration, in open areas prone to fire risks, where rainfall exceeds 2000 mm, hardy evergreens may be planted (Memecylon edule, Syzygium cumini, Aporosa lindleyana, Alstonia scholaris etc. may be planted along with, more tolerant deciduous species, preferably N-fixing legumes like Xylia xylocarpa, Pongamia pinnata, Pterocarpus marsupium etc.) may be planted.
2. Early succession species should have reasonably long seed dormancy as early germinating (recalcitrant) species require special care.
3. Forest ecosystem restoration in high rainfall zone may aim at climax ecosystem re-establishment with high share of evergreen species, paving way for return of endemics, both floral and faunal, through natural processes and careful introductions.
4. As vertical stratification in the forest canopy increases, shaded conditions intensify, runoff water decreases, organic debris on the ground increases, soil regeneration and humus integration render sponginess to the ground progressing enabling the low bulk density soil to absorb, retain and release water into the dried-up stream networks perennially.
5. As darker shade and dampness increase return of endemics, both among trees and in the undergrowth, the rain forest animal species get more promising habitats.
6. In planned restoration programmes, simulating natural succession process, utility species may be introduced such as Garcinia spp., Cinnamomum spp., wild mangoes, jackfruits, rattan canes, palms, Ochlandra reeds, balsaminous trees (eg. Canarium strictum, Vateria indica, Ailanthus malabarica etc.), wild pepper, long pepper, medicinal plants etc. Nectar species promoting honey production in the forests and pollination services in the farms are several for introduction during different stages of restoration.
7. Predominance of fruit and edible seeds producing species will gradually reduce wild animals raiding into farmlands, which currently is happening on a major scale.