For Monica Zunnyi-Abu, hosting her son's 10th birthday party in an unremarkable park in Nigeria's financial capital Lagos proved to be a revelation.

The small, rectangular Ndubuisi Kanu Park includes a well-groomed lawn, a jungle gym, a basketball court and some umbrella-shaded seats, with two small canteens at each end.

Surrounded by government buildings and a busy road, the park offers little seclusion from the constant noise of a congested and over-crowded megacity that is home to some 20 million people.

But it represents the kind of green space that is flourishing across this west African city -- typically tiny and tucked amid masses of concrete.

The Lagos state government admits that its green initiative has been hampered by a shortage of space, and has tried to install parks wherever possible, on congested roundabouts or patches of vacant land under bridges.

Ndubuisi Kanu Park is just a few hundred square metres in size but despite the lack of peace and quiet, Zunnyi-Abu said it was exactly what she was looking for.

"We never have parties in such open spaces," she told AFP during an after-school visit to the park with her two children, aged 10 and eight.

Typically, she said, her children go to parties in stuffy reception halls or at private homes enclosed by high walls designed to keep strangers out.

"I wanted to do something different for the kids," she said, explaining that in her social circle, hosting events in a public space was a foreign concept.

"It was really cool," she said. "We couldn't get the kids out of here. They wanted to play and play. Families were elated."

- Paradise lost -

Land pressures caused by population growth have gobbled up a lot of the former parkland in sprawling Lagos.

Woeful planning under decades of military rule meant few of the city's original green areas were protected.

More than 80 parks have been installed since military rule ended in 1999, said Lagos state Environmental Commissioner Tunji Bello, who has spearheaded the greener Lagos drive.

He recalled weekends in his youth spent in Ikoyi Park, a lush oasis on the city's upmarket island district of the same name.

Retired civil servant Michael Dosu Oyelude said for Lagosians, the Ikoyi Park was seen as a gift left by British colonialists after independence in 1960.

He described it as "a very huge and open space... a haven" used for picnics and even weddings.

It was full most weekends in the 1960s and 1970s, until "the military regime started turning it into an estate", he added.

Ikoyi Park is now Parkview Estate, which resembles a US gated community. Access is restricted by private security guards who work for the tenants, most of whom pay several thousand dollars a month in rent.

Bello, who has served two terms as environment commissioner, conceded that recreating something similar to Ikoyi Park will be tough, given the high land values in places like Ikoyi and with developers racing to build high-rises.

So, he said, his office has had to think small.

"We are trying to find those little spaces... everywhere," he said.

Bello's roster of 80 parks includes a garden on the Falomo roundabout, hardly a place conducive to sitting down and enjoying the smell of freshly cut grass.

Under a bridge that links Ikoyi with the commercial district Victoria Island, it is regularly one of the most congested intersections in the city.

But it has been used for public gatherings, hosting a memorial display for the 219 schoolgirls kidnapped by Boko Haram as well as anti-government "Occupy Lagos" rallies in 2012.

- Sedentary city -

The flourishing of parks may also help tackle a problem that many associate with the West but which also appears to be on the rise in Lagos: childhood obesity.

A 2012 study co-authored by the paediatric departments at the University of Lagos and Lagos University Teaching Hospital found that worrying levels of children were either overweight or obese.

A key conclusion from the study was that while many of the 845 children (aged nine to 18) sampled had access to a playground in the city, those facilities were "generally poorly utilised".

The report did not address the reasons for limited playground use but Bello speculated it was linked to negative lifestyle trends.

Traffic in Lagos can be interminable and appears to be getting worse after successive federal governments struggled to improve public transport.

Nigeria, Africa's top oil producer, does not produce enough electricity to meet public needs, so noise pollution has also worsened through increasing reliance on generators.

In short, people spend so much time and effort getting to where they have to go -- be it from school or work to home -- the desire and energy to spend time in parks has diminished.

But, Bello said, resistance to spending time in parks was "evolving" and noted that most of the parks in the city were well used.

Zunnyi-Abu said her children marvelled at the places they could play during visits to the United States, but, she said, in Lagos, "things are getting better".