New Delhi: Delhi forest department has got its first-ever 10-year work plan to improve and preserve its ecology and maintain and manage its forests and animal species, while weeding out threats to them.The plan, which focuses on scientifically managing the capital’s biodiversity, will be in force till 2036-37. It has been drawn up by Dehradun’s Forest Research Institute.It focuses on systematically removing three major invasive tree species — prosopis juliflora (vilayati kikar), eucalyptus and leucaena leucocephala (river tarmarind or subabul), which together account for nearly 40% of the capital’s forest growing stock.The objective is not general tree felling, but targeted eradication of these invasive species to make space for native vegetation. These species are a threat to Delhi’s biodiversity and soil health, don’t support propagation of wildlife or animals, and suppress the regeneration of native species. The plan advocates their elimination over the next 10 years.“Prosopis juliflora will be removed using the cut-rootstock method, while eucalyptus and leucaena will be cleared through felling.
Operations may be carried out manually or mechanically depending on the condition of the sites,” the plan states.The process of removal will be phased, with only 20% of a given forest section treated each year, allowing gradual clearing over five years while minimising ecological disruption. “The areas that are cleared will be replanted with fast-growing native species at a high density (about 2,500 plants per hectare),” the plan adds.It also suggests exploring biological control measures — such as seed-feeding beetles (algarobius) and pathogens, including fungi like fusarium oxysporum and alternaria alternata, and bacteria like pseudomonas fluorescens — to weaken the invasive populations and reduce their spread.“Algarobius prosopis and algarobius bottimeri are potential biological control agents that target the seeds of prosopis juliflora.
These beetles have been used in other regions to reduce the seed bank of the plant, thus limiting its spread. In Delhi, the efforts could focus on identifying and introducing these beetles to curb the proliferation of new seedlings,” it states.Fungal pathogens like fusarium oxysporum and alternaria alternata have shown promise in causing diseases like wilt and leaf spot in prosopis juliflora. Research and trials in Delhi could focus on harnessing these pathogens, either through direct inoculation or by enhancing natural infections in existing prosopis stands, the plan states, adding that bacteria like pseudomonas fluorescens have been identified as potential biocontrol agents.Algarobius prosopis and algarobius bottimeri are native to North America and Mexico and have been used in Africa and Australia to control invasive species of trees. They can induce diseases in prosopis juliflora, leading to weakened plants that are more susceptible to other control measures, the plan asserts.It also stresses regeneration or the ability of forests to naturally replenish themselves. “The presence or absence of regeneration serves as a key indicator of a forest ecosystem’s health.
If a forest shows poor or inadequate regeneration, it suggests underlying health issues. This information helps forest managers implement corrective actions, utilising appropriate silvicultural methods to promote regeneration and tackle factors that hinder its growth and establishment,” the plan states.However, the state of regeneration of most of the native species across different forest ranges in Delhi is very poor, it notes.
“Not a single range has shown good regeneration of the species. Only two ranges have demonstrated fair regeneration and that too of only a couple of species: morus alba in Central Forest Range and wrightia tinctoria in Asola Bhatti Forest Range,” it states, while stressing that regeneration improves significantly in protected areas, reinforcing the need for sustained protection alongside restoration efforts.The plan also suggests measures for ecological restoration of the Ridge, maintaining soil moisture and curbing its erosion by planting grasses like typha and bamboo along the Yamuna, and constructing silt retention dams and ponds. It also suggests increasing regeneration of major native species of plants, measures to conserve water bodies and plans to avoid pollution by making layered plantations and grasslands near the river, avoiding forest fires, enhancing patrolling to avoid misuse of forest lands and demarcating boundaries.
