Evergreen Forests: A Reminder from an Olea Tree

During the summer of 2024, I was walking through a patch of rainforest near Makkimala village in Wayanad to study the ecology of migratory butterflies in the Western Ghats. The hills are covered in dense rainforests, with trees so large even two people together cannot embrace them. The forest is home to towering sirpoon trees, white cedar, and wild durian, all standing in full grandeur.

Despite the intense summer heat, the thick green foliage overhead absorbed most of the sunlight, allowing us to walk comfortably in the shade. The thought that the same sun scorches some distant desert while barely penetrating this rainforest canopy made us appreciate the trees even more. This humid, lush forest is a refuge for countless creatures, even in peak summer. Despite heavy rains (estimated at 5,000 mm annually), the soil on these steep slopes remains undisturbed, covered in a thick carpet of leaf litter. Beneath this protective layer, countless fireflies, termites, millipedes, and moth cocoons lie dormant, awaiting the arrival of the monsoon.

Closer to Makkimala, the trees were younger. On gentler slopes, large trees are found only sporadically. Olea trees (Olea dioica) dominate the forests near the village. Olea is not a fast-growing species that establishes in the early stages of a regrowing rainforest, but it is well-adapted to disturbed habitats in the southern Western Ghats.

While walking through the forest, we noticed a majestic, smooth, ash-coloured ben teak tree (Lagerstroemia macrocarpa), with no leaves on it, standing amidst an evergreen forest. We wondered how this deciduous tree (one that sheds leaves annually) found its place here amid the evergreens (trees that don’t shed leaves).

Our 60-year-old companion from the Kurichya tribe provided an explanation: “During my childhood, this area was used for shifting cultivation. The forest was cleared and burned for farming. At that time, this tree stood alone amidst our ragi cultivation. Once cultivation ceased, the forest reclaimed the land.” Only fire-resistant deciduous trees survived in the open farmlands that were regularly burned. This gave me an answer to a question I had pondered for years — why do massive deciduous trees line some of Wayanad’s public roads, while most of the younger trees in surrounding plantations are evergreen species? I would guess that the semi-evergreen forests — a mix of evergreen and deciduous trees —seen in Wayanad today have been shaped in a similar way. They represent forests that regenerated after the land was brought under protection through various forest laws. 

Why Evergreen Forests Are Missing Where They Should Thrive

Since around 2004, I have walked through almost every forested region in Kerala. I have closely observed and studied the diverse forest types of the Western Ghats: evergreen forests that dominate the western slopes and other high-rainfall areas; shola–grassland ecosystems at higher elevations with strong winds; moist deciduous forests found on gentler slopes near human habitations; and the dry deciduous forests in low-rainfall zones, especially along the eastern slopes of the ghats. I have encountered rare and threatened swampy habitats, such as the well-wooded myristica swamps and open vayals (fields) with grasses found at various altitudes. The riparian forests, lined with evergreen trees along the banks of certain rivers, are another distinctive feature.

I’ve often wondered why semi-evergreen or moist deciduous forests dominate certain areas between 300 and 500 metres on the western slopes of the Western Ghats while evergreen forests seem to persist only in relatively undisturbed patches.

In tropical regions receiving over 2,000 mm of rainfall, undisturbed areas naturally support rainforests. If left untouched, and if wildfires are prevented, evergreen species should dominate the forests over time. The numerous sacred groves in low-elevation areas across Kerala provide evidence of this phenomenon. However, the widespread presence of deciduous forests in the Western Ghats, especially along the western slopes and the high rainfall areas such as Wayanad, is likely a result of prolonged human intervention. Recent studies in the northern Western Ghats have found that the seedlings that thrive in human-disturbed forests are mostly deciduous species.

Rainforest trees (evergreen) have limited ability to survive fires, whereas deciduous trees, adapted to warmer climates, possess a thick bark and high fire resistance. Repeated fires, therefore, wipe out evergreen plants and permit the growth of deciduous forests. 

Wayanad’s topography

The eastern part of Wayanad, including the Wayanad Wildlife Sanctuary, consists primarily of deciduous forests. Most of the sanctuary receives over 2,000 mm of rainfall. So why do deciduous forests dominate Wayanad despite receiving substantial rainfall? No extensive scientific studies have been conducted to answer this question. Moreover, the ecological history of Wayanad remains largely unexplored.

Before British rule and large-scale migrations, agriculture in Wayanad was primarily subsistence-based, focused on rice, millets, and tubers. Rice cultivation dominated, with farmlands confined mainly to wetland fields; upland farming was minimal. Since there was no commercial agriculture, extensive land clearance was unnecessary. However, shifting cultivation, which involved burning tracts of forests in rotation, was widely practised. This practice likely affected forests near settlements more than remote forests.

The lowland forests of the Wayanad sub-plateau have been used by humans for centuries. Indigenous communities of Wayanad maintained close interactions with the Deccan Plateau, a connection still evident in cultural practices today. Until recently, people from the Deccan travelled through these forest paths with their livestock.

How Fire and Felling Reshaped the Western Ghats

Walking through forests inhabited by elephants and large carnivores has always been risky. To navigate safely, in the past, people likely used fire to improve visibility and reduce threats. Over time, this practice created more open spaces, making movement easier while encouraging the growth of grasses that benefited both wild herbivores and livestock.

Large-scale tree felling and repeated fires in the colonial period transformed Wayanad’s forests from evergreen to semi-evergreen and deciduous. The Pakam Kotta region, for example, which is considered sacred by indigenous communities, hosts a small patch of evergreen forest surrounded by deciduous forests. Its sacred status might have protected it from intentional burning. Even within the vast deciduous forests of Wayanad Wildlife Sanctuary, small patches of evergreen vegetation persist near wetlands, sheltering rare species like the Malabar tree-nymph butterfly, the white-bellied blue flycatcher, the grey-headed bulbul, and even threatened Syzygium stoksii trees. These forest remnants hint at the potential for rainforests to recover if conditions allow.

Despite conservation efforts, human-induced forest fires remain a persistent issue in the Western Ghats. Fires are often lit due to fear of wildlife, as acts of retaliation following human-wildlife conflict, enforcement actions by forest officials, or even to improve visibility while moving through forests — particularly by forest-dependent communities. Interestingly, some indigenous groups believe that controlled burning benefits wildlife by promoting fresh grass growth, which supports herbivores and, in turn, carnivores. While certain plants and animals may benefit from fires, rainforests — rich in biodiversity — struggle to regenerate in fire-prone landscapes, ultimately harming the ecological integrity of the Western Ghats. However, with recent conservation efforts, forest fires have decreased, but another danger has emerged — fast-growing invasive plants spreading unchecked in the degraded open areas, further suppressing native species in the forests.

In Pathiri Reserve Forest in Wayanad, the forest department extensively cleared bamboo forests about 15 years ago after its mass flowering event. Since then, the area has been left undisturbed. Today, pioneer evergreen species are recolonising these forests. Similarly, in Kerala’s former teak plantations, where fires have been absent for years, several evergreen tree species are now regrowing above the canopy of teak trees. Some erstwhile monoculture teak plantations in the forests of Parambikulam Tiger Reserve have already begun reverting to evergreen forests.

Green in the Dry: A Sign of Resilience

In the summer of 2024, while walking through a dry deciduous forest at the easternmost edge of Wayanad Wildlife Sanctuary, I noticed a medium-sized olea tree standing by the path. In a landscape where all the other trees had shed their leaves, this single evergreen tree stood out in its vibrancy. It reminded me of the forests near Makkimala village. By the end of summer, the olea tree will be laden with thousands of fruits, providing food for many birds. The birds, in turn, disperse seeds across the dry forests along with their droppings. In the monsoon, some seeds will sprout and emerge from the dense thickets of lantana (Lantana camara). The young olea saplings, having inherited the resilience of their parent tree, might also survive the harsh summer in that area, receiving less than 1,300 mm of rainfall. If these young trees are not burned down in their early years, then a decade later, even if the forest does not transform into a full-fledged rainforest, it could still become a wetter forest, such as a moist deciduous forest — one that provides more shade and supports a greater diversity of life than a dry deciduous forest. This lone olea tree reminds us of what evergreen forests can be.

How Thoughtful Intervention Can Restore Wild Spaces

As the global climate crisis threatens to upend Wayanad’s climate and economy, we may not be able to stop the effects entirely. However, we must at least ensure the existence of more evergreen forests in eastern Wayanad to combat the increasingly dry summers. These forests can help cool Wayanad by converting the dry eastern winds from the Deccan Plateau into moisture-laden, cooler breezes.

Once, human activities contributed to the drying up of forests, rivers, and streams. In the future, human efforts could also play a role in reviving them. Given Wayanad’s current climate conditions, can the forests regain their greenery? Can human intervention help in this process?

The answer lies in the above map of Vadakkanad village within the Wayanad Wildlife Sanctuary. Here, private lands maintain green agricultural crops with scattered evergreen trees even during the summer, while the adjacent protected forest appears starkly different — with leafless trees, invasive species, and drying vegetation. This contrast illustrates how human intervention, when thoughtfully managed, can sometimes help restore greener wild spaces. The time to scientifically plan and implement ecological restoration has already passed, and rising human-wildlife conflicts are a constant reminder of this urgency.

Restoration and Conservation: The Need of the Hour

Wild nature has the ability to heal itself. Therefore, conservation today requires us to allow native vegetation to grow naturally and restore biodiversity to bring back the resilience of forests. The importance of restoring forests that were once converted into monoculture plantations and the urgency of preventing wildfires become even clearer when viewed in the context of rising temperatures in the Western Ghats.

Photo sources: cover, Olea dioica, flowers, bark, full tree, forest fire.