Green causes have gained prominence here over the past two decades, and yesterday's debate on the Parks and Trees (Amendment) Bill showed just how passionate some MPs can be about nature and wildlife issues.

The Bill, noted longtime wildlife activist Louis Ng (Nee Soon GRC), was a "milestone in our efforts to protect Singapore's biodiversity".

He recalled that Acres, the animal charity he started, rescued more than 3,000 wild animals last year alone. Yet the most common response he gets when he tells Singaporeans about this is: "Singapore got wild animals meh?"

Other MPs - nine spoke on the Bill - cited examples aplenty.

Mr Darryl David (Ang Mo Kio GRC) said that in spite of its busy maritime traffic, the Singapore Strait's diverse marine life includes the hawksbill turtle, Indo-Pacific humpbacked dolphin, and blacktip reef shark.

Mr Henry Kwek (Nee Soon GRC) noted how, on a recent visit to Thomson Nature Park, he came across the greater slow loris, banded leaf monkey, and the sunda pangolin. His group also chanced on a baby big-eye green whip snake. He hopes more young people can be enticed to visit parks and enjoy the experience.

Their encounters and exchanges in the House are a reminder that a fine balance has to be struck between protecting parks, nature reserves and their flora and fauna as urban development encroaches on their fringes.

Several MPs felt the changes - to protect the first marine park at Sisters' Islands, and to make it an offence to release or abandon an animal into a body of water that leads to a nature reserve - could go further.

Mr Ng wanted the law to prohibit the release of exotic species anywhere - on land and in water. Animals, after all, have the freedom to move to nature reserves.

Non-Constituency MP Leon Perera said the changes did not address the issue of invasive species entering the reserves by chance - such as non-indigenous decorative plants favoured by condominium developers reproducing in the reserves, or exotic pets escaping accidentally.

NCMP Daniel Goh spoke at length about how he was disappointed with the scope and scale of the changes.

He saw the need to designate Sisters' Islands Marine Park as a nature reserve. That would afford it greater protection. He wanted a buffer zone to protect the area in the event of incidents like an oil spill.

And he wondered whether the marine park might, one day, become an eco-tourism theme park - and sought assurances that there were no plans for such a development.

Responding to the MPs, Senior Minister of State for National Development Desmond Lee said Dr Goh's "harbinger of the turning of the marine park into Disneyland... is certainly not at all in the plans".

His ministry, Mr Lee said, would also find ways to keep the younger generation engaged and excited about parks, citing undergraduate Sean Yap who started a Facebook album - Real Life Pokemon of Singapore - to show the similarities between Pokemon characters and native plants and animals here.

Mr Lee also said invasive species are a perennial concern. This is why buffers have been established around nature reserves to protect them "from the dessicating effect of buildings and concrete and traffic". Such buffers also give NParks the opportunity to remove alien species "that have been deliberately or accidentally released from these developments into the nature reserves".

Singapore's approach to nature, while pragmatic and driven by development needs, has sought to integrate development with nature.

As Mr Lee noted, Singapore is a biophilic city. The term describes how humans are hard-wired to need connections with nature and other forms of life.

In some other countries, the approach is to "prohibit a whole series of activities and try to tell people 'Please don't go there, minimise contact, keep a distance, let nature thrive'.

"In Singapore, it's the converse. We're a city in a garden - the city envelops our nature reserves, our nature parks, envelops our biodiversity," Mr Lee said.

"We have to be biophilic ... We have to be good custodians and stewards of our biodiversity - not just keeping it away at arm's length through legislation and prohibition, but to educate, to excite, to enthuse people to care about the plant and animal species that make us a very special place."

Parliament sittings see a stream of students and others in the public gallery, and hopefully those watching yesterday's debate will be spurred to find out more about what and where Singapore's wild animals and plants are.

The protection now afforded to Singapore's first marine park, and more developments to safeguard the natural environment, should give Singaporeans a chance to discover how important it is that nature should retain a central place in a continually developing city.