Officials say the botanical garden around the Napier Museum was never intended to be a picnic or holiday spot.

The pollution might not be obvious. But it is definitely there and has possibly taken an indefinite toll on the natural environment of the century-old botanical garden surrounding the 130-year-old landmark Napier Museum and Zoo here.

An unprecedented number of holiday makers had visited the zoo this festival season. Despite their best efforts, Museum authorities could hardly prevent the crowds from trampling on the grass and damaging flower beds. They also had to hire extra manual labour, including trucks, to remove the huge amount of litter lakhs of visitors left behind in the past one week.

A Museum employee told a set of morning walkers on Tuesday that ice-cream cups, ice-candy covers, styrofoam beakers, synthetic containers, cigarette packets, matchsticks, the occasional liquor bottle, exploded balloons and plastic trinkets made up much of the urban waste that was painstakingly removed from the grounds.

The amount of debris left behind by the crowds seemed to be more than the quantity of fallen leaves and garden debris that covered the expansive garden.

The Museum and Zoo authorities had recently launched a series of apparently successful initiatives to reduce the considerable volume of non-biodegradable urban waste deposited daily at the garden. The effort was to protect the botanical garden’s original environment and its wealth of rare and old trees.

Officials said the festival crowd that swamped the Museum grounds was so huge that they were only partially successful in preventing visitors from littering the garden.

The authorities had set up drinking water fountains at different points in the garden last year to save visitors the trouble of lugging around bottled water and prevent littering.

The authorities pointed out that plastic was hazardous to botanical gardens in many ways. For one, it caused stray dog and crow menace and aided the profuse breeding of mosquitoes, rats and cockroaches.

Certain “green regulations” insisted that botanical gardens be insulated from all manners of littering. In 2011, the Kolkata High Court had criticised the Shibpur botanical garden authorities for allowing garbage to accumulate in the garden premises.

Officials said that government botanists need to scientifically assess the impact of uncontrolled crowds and urban pollution on the valuable trees and shrubs in the garden. Automobiles should not be allowed into the premises and the eateries operating inside the garden should be shifted out.

They said the botanical garden was never intended to be a picnic or holiday spot. It was designed to aid students interested in plant taxonomy, the science that describes, classifies, identifies and names plants. The garden hosts several rare and exotic plant and tree varieties.

The huge rubber tree near the first gate, believed to be planted in the 1870s, is perhaps as old as the garden itself. Arguably, one of the latest additions to the garden is the sapling of a Paradise Tree (Simarouba or Laxmi Taru). It was planted last year near the second (Kanakakunnu palace side) entrance to the historic garden.