Three years after Delhi government announced a plan of getting rid of Prosopis juliflora or Vilayati Kikar in the Central Ridge may finally takeoff with the Delhi cabinet approving its replacement with native species at a cost of Rs 12.6 crore in the initial phase. Scientists and experts have been emphasizing on the kikar’s environmental and other impacts as it a very aggressive invader and replaces native vegetation and takes over rangelands. In case of Ridge in central Delhi, it has done so.
The Ridge in Delhi is spread over 7,777 hectares. Of this over 80 per cent is covered by vilayati kikar. An area of 482 acres is to be redeveloped and a community of 30 different native plant species will be planted.
How it came to Delhi?
By all accounts, the tree was first imported into India in 1877. The place where it was first planted, as an exotic and decorative tree by the British, was perhaps Calcutta (now Kolkata) — their colonial capital. The tree brought from Mexico got popularly called the Mexican Mesquite. So, the Mesquite seems to have arrived in Delhi when the Vice-regal Lodge (present-day Rashtrapati Bhawan) was being built. It is said that Messers Baker and Lutyens were not very happy with the stark rocky backdrop to this symbol of imperial grandeur and so the horticulturist William Robertson Mustoe was given the responsibility of ensuring that the rocky landscape was dressed up in green by the time the Vice-regal Lodge was completed.
Accordingly six varieties of trees, including Sheesham, Jungal Jalebi, Siris, a desert Eucalyptus from Australia and the Mesquite, incidentally none of them belonging to Delhi, were tried out on the ridge. The only one that survived was the Mesquite. And this was the beginning of the demise of a large variety of trees, bushes, and shrubs that were uniquely suited to the primarily semi-arid environment and the rocky landscape of Delhi.
The systematic plantation of the Mesquite on the Central Delhi Ridge incidentally came at the behest of Harding –Viceroy between 1910 and 1916. It was the same Harding who was grievously injured in a bomb attack while he was passing through Chandni Chowk, astride an elephant in a regal procession commemorating the shifting of Capital to Delhi in 1912. The bombers had hidden behind a tree and all the trees in Chandni Chowk were cut down when Delhi was punished for the bomb attack. The canal that passed through Chandni Chowk was also bricked over and closed.
So Harding’s legacy includes not only the chopping down of all the trees of Chandni Chowk but the long term decimation of the flora of Delhi as a consequence of steps for greening the ridge initiated at his behest.
There are three reasons for the rapid growth of the Mesquite in Delhi and in India. One, the tree was brought to India as seed, none of the natural controls, insects, bacteria, diseases of the tree were imported and so the tree grew without any ecological checks on its growth. Two, it is a desert tree and therefore the semi desert conditions suit it ideally and three, it releases toxins in the soil through its roots and thus inhibits the growth of other vegetation and soon, like a true agent of imperialism, it wipes out all competition, becoming lord and master of all it surveys.
Know More About the ‘destroyer’ kikar?
Prosopis juliflora is a thorny shrub 3-5 m or tree growing up to 15 m height. It has a thick rough grey-green bark that becomes scaly with age. The plants are often multi-stemmed and furnished with abundant large and very sharp thorns measuring up to 5 cm. The tree is deeply rooted. The stems are shaped in a “mild zigzag” way with one or two stout thorns at each turn of the stem.
The flowers are fragrant golden-yellow, dense spikes about 5-10 cm long. The fruit of P. juliflora is a cylindrical or slightly irregularly curved green pod which turns yellow upon ripening. It is 10-20 cm long, sweet to taste and contains 10-20 hard oval or elliptic seeds (2.5-7 mm long) that are difficult to extract..
Its roots are able to grow to a great depth in search of water: in 1960, they were discovered at a depth of 53 meters (175 feet) at an open-pit mine near Tucson, Arizona putting them among the deepest known roots.
This plant reproduces through seed, often once they have passed through the digestive tract of browsers – such as goats, cattle, camels and some wild herbivores. It is spread along water courses and run-off areas during periods of rain and then spreads laterally from these sites.
Various Prosopis species have beneficial qualities which include erosion control, shade, fuelwood, building materials, and pods for animal and human consumption in arid and semi-arid regions. The fact that there are clear economic uses to this species but severe negative consequences of P. juliflora invasion makes this a conflict of interest species.
Environmental and other impacts
Prosopis juliflora can be a very aggressive invader and replaces native vegetation and takes over rangelands. Negative effects include complete loss of pasture and rangelands for both domestic and wild ruminants, losses due to access to water and the destruction of fishing nets by the thorns, and illness and death of livestock due to eating P. juliflora pods and being pierced by the sharp and stout thorns. Other impacts are loss of cropland, the costs of repairing tyres punctured or destroyed by thorns, and doctor’s bills for treating thorn wounds. Dense stands of P. juliflora can block irrigation channels, obstruct roads and block smaller trails completely affecting access to pasture, croplands, water sources and fishing areas.
Prosopis species are salt and drought tolerant with deep roots which tolerate dry as well as waterlogged soils. Seed production is prolific. Trees rapidly form dense thorny thickets that reduce biodiversity (Weber, 2003). Invaded grasslands are transformed to woodland and forests. Loss of grass cover under canopies may also promote soil erosion. It has massive impacts upon water resources. The tree resprouts easily after damage (Weber, 2003).
Crop farmers from Chemonke village, Kenya, have had to seek alternative settlement elsewhere because they have lost their land to P. juliflora invasions, often resulting in conflict with established communities, (Mwangi and Swallow, 2005). Surveys of local communities around Lake Baringo revealed that 85-90% of respondents to a questionnaire favoured complete eradication of invasive Prosopis species (Mwangi and Swallow, 2008). In another study Maundu et al. (2009) found that 64, 79, and 67% of respondents interviewed in the Garissa, Loiyangalani, and Baringo areas of Kenya, respectively, said that life would be better without Prosopis. Over 90% of livestock owners in eastern Sudan regard invasive Prosopis as a liability and pastoralists in Ethiopia refer to Prosopis as the “Devil Tree“.