Long before global warming became a topic of hot discourse worldwide, certain traditional practices of humans, like home gardens, have served as natural ways to maintain environmental equilibrium. Home gardens are defined as intimate, multistory combinations of various trees, plants, herbs and crops, sometimes in association with domestic animals, around the homestead.
They cannot be confused with ornamental manicured (home) gardens with exotic and non-native species. A popular practice in many parts of South Asia, Southeast Asia, Latin America and Africa, home gardens are left to grow wild, around homes and sustain their owners with everything from food and fuel to shade during summer months. Beyond what is apparent, these tropical home gardens provide a range of invisible ecosystem services such as holding species diversity, acting as carbon sinks and windbreaks, replenishing water tables and managing hydrological cycles.
Home gardens are a type of land use system developed mostly by subsistence farmers. The south Indian state of Kerala has a tradition of home gardens that has served as a topic of study for researchers in different parts of the world, particularly for the biodiversity they hold, said B Mohan Kumar, Vice-Chancellor of Arunachal University of Studies who co-authored the book on home gardens in Kerala titled Tropical Homegardens: A Time-Tested Example of Sustainable Agroforestry.
He explains that these home gardens have traditionally been a type of agroforestry and are similar to the home gardens found extensively in Sri Lanka and Java in Indonesia. In most cases, these intensively managed systems form the main source of nutrition and income for the household.
But what truly sets the Kerala home gardens apart, is the diversity of species.
Kerala-based environmentalist K V Dayal has developed a unique home garden in his 1.5-acre land following an agroecological design wherein 10% of the land is maintained as a natural ecosystem with a manmade hill and a pond, while 90% is a cultivated ecosystem or a food forest.
This mini-forest around his home fulfils fivefold objectives of acting as windbreaks, replenishing groundwater table, providing food for all living things that depend on it, conserving biodiversity and creating a microclimate. Dayal’s home garden boasts of over 200 species of trees, plants and herbs, a variety of avifauna, animals like monitor lizards, civets and insects and reptiles.
A study on the biodiversity of 75 home gardens in Kerala, revealed that the biodiversity of home gardens studied was comparable with natural forested regions in the area. A study published in 2021 conducted on a one-hectare area of home gardens in Kerala found that 992 trees from 66 species belonging to 31 families of which four were endemic and one each were vulnerable and endangered. The diversity indices obtained were closer to those of a forest ecosystem.
What does it mean? The species density of a land-use system can determine the carbon sequestration potential of the system. Home gardens with high species density are found to have better soil organic carbon stock, making them a key ally in our efforts to reduce carbon in the atmosphere.
“Sunlight is the life of the soil. It reaches the soil through photosynthesis in plants. Plants act as carriers of carbon to the soil. The carbon that needs to be in the soil to nourish it is now in the air, leading to global warming,” illustrates Dayal.
Since sunlight is a fundamental natural resource, the idea of his home garden is to capture it fully through trees and plants and make the most of it.
Invisible ecosystem services
The 2005 Millennium Ecosystem Assessment Report breaks the ecosystem services of nature into four categories – provisioning services such as food and water, regulating services such as flood and disease control, cultural services such as spiritual, recreational, and cultural benefits and supporting services such as nutrient cycling.
Home gardens in Kerala tick all these boxes. Mohan Kumar lists a range of contributions that home gardens provide people. “Provisioning services include food production in terms of fruits, nuts, grains, herbs and medicines,” he elaborated. “Traditionally, fuelwood for the kitchen came from the home garden and served as an important source of domestic energy. Home gardens also provide timber as a source of income, medicines for home use and cut and carry fodder for the livestock.”
In the book Tropical Homegardens… he wrote about how home gardens provide various supporting and regulative services as well. “Climate change has emerged as a major environmental problem at the turn of the century. The principal reason is the rising carbon levels in the atmosphere. The best way to mitigate this is by trapping carbon in the air with the help of vegetation or biomass,” said Kumar. The carbon thus trapped will increase the organic carbon in the soil, thereby improving the health of the soil. Home gardens, thus have the potential to sequester carbon.
In his studies on home gardens, Kumar finds that the carbon concentration above the ground in home gardens was 60 tonnes to 70 tonnes of carbon per hectare and the organic carbon stock in the soil was 80 tonnes-100 tonnes carbon per hectare in 1m depth of soil.
The large amount of litter produced in home gardens, aid nutrient cycling of the soil and act as nitrogen fixers making the soil fertile. “Some common tree species in home gardens like Gliricidia sepium have the ability to produce nitrogen,” he added.
Apart from these services, home gardens have the potential to improve the hydrological cycle by recharging water tables and replenishing aquifers. It also has the potential to reduce soil erosion and act as windbreaks, he added.
In many parts of the world, including Kerala, home gardens provide various cultural services too, by acting as recreational spaces for families and communities. They also house religiously important plants and trees and have, in some cases, sacred groves, too that are worshipped and preserved.
Future of home gardens
A recent workshop report published by 50 of the world’s leading biodiversity and climate experts from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services and the Intergovernmental Panel on Climate Change, emphasises the importance of looking at biodiversity loss and climate change as an interconnected challenge.
The report notes that restoring carbon- and species-rich ecosystems is among the cheapest and the quickest nature-based climate mitigation measures to implement. This would not only offer the much-needed habitat for plants and animals, enhancing the resilience of biodiversity in the face of climate change but also has other benefits such as flood regulation, coastal protection, enhanced water quality, reduced soil erosion and effective pollination.
The number of home gardens in Kerala are on the decline. A researcher at the School of Environmental Sciences, Mahatma Gandhi University, Kerala, Babu Padmakumar who undertook the 2021 study on home gardens concludes by saying, “Urbanisation and the resulting fragmentation of traditional landholdings and economic activities like converting agricultural lands to monoculture plantations like coconut and rubber have considerably reduced the size and diversity of home gardens. In the absence of enough research and understanding about home gardens as a climate change solution or the political will to conserve them, we are staring at a situation where nature’s simplest solution to climate emergency could be lost forever.”
This article first appeared on Mongabay.