There are some trees in the Western Ghats of India which almost always have water around their ankles.
The water comes from streams and rivers which flow into low-lying areas and valleys to form a swampy environment.
To adapt to these water-logged conditions, the trees have evolved to stand on their tip-toes. They have stilt roots, much like the those of mangrove trees, and knee roots or pneumatophores – roots that surface out of the soil and water and loop back into it. These roots are spongy, allowing the roots to breathe underwater. As the knee and stilt roots age, they become woody and flattened and form what are known as ‘flying buttresses’ – wavy curtains of wood snaking through the soil. The profusion of aerial roots is what strikes you at once in this strange ecosystem. Navigating through the tangle of roots makes me feel as though I am in a woody jungle gym.
These are the Myristica swamps. Once forming a continuous chain across the Western Ghats, they are confined to very small pockets in low-elevation evergreen, semi-evergreen and moist deciduous forests. They are found now only in small tracts in Kerala, north Karnataka and parts of Goa. Many of them occur in sacred forests, but only a small portion of their distribution occurs in 10 of the 48 protected areas in the Western Ghats.
A couple of species, Myristica magnifica and Gymnacranthera canaria, belonging to the genus Myristicaceae are the most common trees found in these swamps. There are also other trees like Myristica malabarica and Elaeocarpus which are tolerant to flooding but do not exclusively occur in swamps. In 2000, a new tree species, Semecarpus kathalekanensis which is part of the mango family, was reported from the Myristica swamps of north Karnataka.
Although the root system has special adaptations to waterlogged conditions, the seeds of the trees in Myristica swamp cannot germinate in water. They remain viable and germinate only when the soil is exposed during the dry season or periods of drought.
The seed, which is very similar to the commercially harvested nutmeg, is eaten by a lot of animals. Many of them are picky about which part of the fruit they eat. Some of them like the Malabar Giant Squirrel and the Lion-tailed Macaque remove the fruit, discard the seed and eat the aril – the fleshy covering of the seed. The Nilgiri Langur eat raw fruits and seeds while rodents like the Malabar Spiny Dormouse and the White-bellied Wood Rat visit at night for the seeds that were dropped on the ground by other animals.
I’m especially fascinated by one particular visitor to the swamps: freshwater crabs. A study carried out in Kerala designed a neat little experiment to understand the role crabs play in helping to disperse the seeds of a Myristica tree. They were found to be secondary seed dispersers, which means that they moved seeds that were dropped or dispersed by another animal, away from the tree. The crabs took many seeds back into their burrow where they were later found to germinate.
Although the Myristica swamps have many seed dispersers, they have such specific habitat requirements that for one species, Gymnacranthera canaria, even seeds dispersed a few metres away from the swamp are unlikely to germinate.
Having very specific habitat and climatic requirements also makes it harder for these trees to adapt to quickly changing conditions. In the past, several of these swamps were converted to rice fields or plantations of areca, coffee and rubber, or were inundated by hydel projects to a level far above what even their stilt roots could manage.
Even now there are a battery of challenges staring down at them: deforestation and diversion of water for agriculture which can lead to a collapse of its ecosystem; changing temperatures and rainfall, which are projected to lead to a reduced habitat that will be suitable for their persistence in the future.
These forests on stilts could become forests on clutches.
If not to marvel and understand more about these forests and their interactions with the environment, the watershed services they provide is reason enough to protect them: the stagnant, sluggishly moving water in Myristica swamps seeps underground and replenishes aquifers. We would be the poorer without them.
As I wade, crouch and climb my way through a Myristica swamp, pausing to look for the source of a loud ‘tik tik tik!’ – the call of a Torrent Frog which is often found in these habitats, I enjoy getting my own ankles wet and look fondly and hopefully at some new Myristica saplings on the forest floor.