Indigenous vs. Introduced Plants : The Ongoing Debate

Few months ago, I stumbled upon an article written by a representative of an ecological restoration firm that has been promoting native plant species for the past decade. The article sparked controversy by suggesting that non-native tree species need not be shunned altogether. Though the statement was not completely wrong, that article raised eye-brows of many nature-lovers as the statement was contradicting the very soul of that organization. 

So how do you decide what kind of tree to plant? Or perhaps, have you wondered, while walking down a city street or strolling through a park, why did we choose to plant a row of non-native Gulmohor or Rain-trees, instead of trees native to our region? This post aims to provide clarity on this topic by exploring the various factors that influence our tree-planting choices. 

At present, there is a debate on whether to plant indigenous trees or introduced/alien trees. Some favor indigenous native trees while others do not seem to bother about the species. But this debate should be considered from an environmental standpoint.

Different plants thrive in different regions of our country according to the nutrients, climate and habitat. These plants and the wildlife that depend on them create a rich ecosystem, and the introduction of an alien plants into this delicate balance is a matter of ongoing debate. Some say that many introduced shrubs, vines & trees that are naturalised in India, are useful. The examples include guava, custard-apple, grapes, sugarcane etc. But it should be noted here that all these plants are grown agriculturally, where their spread is controlled, carefully maintained. Furthermore, not all introduced plants are non-invasive or benign to the ecosystem.

Proponents of introduced trees argue that they provide shade, oxygen, and visual appeal through their colorful flowers. However, the problem arises when a single introduced tree species outcompetes ten native trees, leading to a tenfold reduction in carbon dioxide absorption and shade. Additionally, habitat loss for birds and pollinators can have devastating impacts on the ecosystem. Introduced species are often free from natural predators & pests, which makes them prone to becoming invasive, out-competing native flora for water and soil. This in turn drives away biodiversity and reduces the chances available for native species, leading to biological pollution. Introduced plants are often short-lived and brittle, making them susceptible to uprooting during storms. The leaves of trees like Eucalyptus and Mangium do not decompose easily and do not contribute to the production of organic fertilizer, resulting in soil pollution. 

While introduced trees like Gulmohar, Copperpod, Jacaranda and Spathodea may look beautiful, their ecological value is negligible. Although a few species of birds may perch on these trees, and pollinators like bees may occasionally be seen on their flowers due to a lack of other flowering species, it would be foolish to conclude that introduced species attract birds and pollinators. Many state governments have banned the cultivation of Eucalyptus due to the large amount of water it absorbs from the soil, which can exacerbate water scarcity issues in certain areas. Introduced species like Gliricidia, Mangium (Acacia Mangium), Earleaf Acacia (Acacia Auriculiformis) and Mesquite (Prosopis Juliflora) were brought to India from Australia and Mexico for rapid reforestation, timber, and fuelwood purposes. However, these same plants have now become a serious threat to ecosystems, competing with indigenous flora and fauna and disrupting nutrient cycling and hydrology. This impacts the overall economic stability of local communities and human health. Many of these species have aggressive root systems or produce a large number of viable seeds, both of which allow the plants to quickly invade the soils outside their growing areas. This resulted in almost destruction of the native Babool (Acacia Nilotica, or recently known as Vachellia Nilotica), which is an important tree species if dry regions. 

Trees native to a particular region have evolved to thrive in specific soil types, rainfall patterns, light availability, seed dispersal mechanisms, and other environmental attributes. In their native environment, these trees may provide cover, food, and habitat for birds, amphibians, insects, and mammals. The tree species that have been living in India for centuries and providing benefits not only to humans but also to wildlife and the ecosystem deserve priority. In fact, there are several fast-growing native trees in India that bear beautiful flowers. Native trees are more adaptable to their growing conditions and more resistant to disease than alien species that have only been introduced in recent decades. You can find the list of native trees here.

Several gardening enthusiasts and nature-lovers derive satisfaction from cultivating rare and uncommon plant species, which are not easily found in their vicinity. In fact, the introduction of new plants is a celebrated activity which delights many gardeners, and attracts media attention. These practices have contributed to scarcity of our own important native species in the urban areas across India. Sadly, it is now increasingly challenging to come across trees like Palash, Sita-Ashok or Kaim in the gardens of many cities. 

In conclusion, it is important to understand the impact of the trees we plant in our region. While non-native species may be visually appealing, they can have negative impacts on the local ecosystem. On the other hand, native trees have evolved to thrive in their environment and provide important benefits to both humans and wildlife. By prioritizing the plantation of native trees, we can promote a healthier and more diverse ecosystem while also supporting the local economy and preserving our cultural heritage. Though there is no need to hate the previously planted and grown non-native trees; at least now onwards, the plantation of any alien or foreign plant must be strongly discouraged. 

Today is 13th anniversary of Gifting Trees... Come, let us all take responsibility to protect our environment and choose the right kind of trees to plant for a sustainable future!