Faulty policies on invasive exotics

Why in the News?

The invasive Conocarpus species of trees have been banned by Gujarat recently due to concerns over its management.

• This comes after the invasive species was banned by Telangana last year.
• There is a possibility of several other states following the suit.
• This can discourage horticulturists and nurseries from multiplying the species for afforestation and landscaping projects across the country over the next year.

Problem with exotic plant species 

1. Exotics are used in urban landscaping projects in particular, for beautification and greening purposes without due attention to the process of selection of species.
2. Many species introduced for greening or ornamental projects eventually turned invasive.
3. Native species which failed to compete for space and soil resources were driven to extinction, which led to significant costs to ensure the management of the invasive species. 
4. Such notable invasive species include:
   1. Eucalyptus
   2. Prosopis juliflora (vilayati kikar)
   3. Acacia mangium
   4. Lantana camara 
5. Conocarpus (buttonwood) trees:
   1. There are two species of
      1. Conocarpus erectus, more widely used in India and is native to South America
      2. C. lancifolius, native to East Africa.
   2. They are easily propagated and multiplied in nurseries through stem cuttings.
   3. Their plantations cause serious pollen allergies and respiratory problems, which has led to civic agencies taking action to ban them.

Reasons for deploying these exotics in the first place:

1. The non-native species often face very few or no pests or pathogens in new habitats.
2. Pest resistance makes their proliferation easy. 
3. They require very little aftercare. 
4. They are not browsed by livestock and thus, favoured for horticultural or landscaping projects.
5. The human population gets familiar with the local pollen calendar and, to a large extent, their immune systems coevolve.

Way forward:

1. Landscape managers have to choose from among native species pools, species that are ecologically appropriate and also meet aesthetic needs.
2. The urban landscaping and agroforestry projects have to refer to existing information on these species before taking up their large-scale use.
3. Urban greening projects should use native species for long-term sustainability. This can marginally increase the costs and effort, but will add immense value in terms of ecosystem services in the medium to long term.

• For instance, the avenue trees in Lutyens’ Delhi from Central India and the Gangetic plain, apart from aesthetics they harbour a large number of native bird species and other dependents.

4. A watch list of plants known to harm native species and ecosystems, and raise public health concerns has to be maintained to monitor import and use of horticultural plants.