Hostile architecture, sometimes called defensive urban design or exclusionary design, is the name for uncomfortable elements built into public features such as park benches or added to building door fronts to prevent homeless sleepers from commandeering the spaces.

This type of hostile design is increasingly showing up on Oahu at bus stops, in Chinatown doorways and in city parks where homeless people tend to congregate.

Uncomfortable, off-putting features are incorporated into private and public structures more and more to discourage other behaviors such as urinating in public, skateboarding and graffiti.

Recently many of the regular park benches along the Ala Wai Canal were replaced with uncomfortable green metal seats capable of holding only two people, tightly packed side by side. Not exactly welcoming places for older pedestrians to rest. And definitely impossible for homeless campers to turn into beds.

The metal seats ignited a firestorm of criticism on the social media site NextDoor, with contributors criticizing the city for being heartless and inhumane to vulnerable homeless people who have nowhere else to sleep. Others complained that the effort to keep homeless people away unfairly adds inconveniences for everybody else.

“I walk along the canal every day. It frustrates me that the city did not consider how uncomfortable the new seats would for the elderly, those with disabilities, and even families with small children,” said Amy Parsons, an Ala Wai Boulevard apartment dweller.

Waikiki resident John Eckels wrote to me in an email Sunday that installing the uncomfortable new seats ignores the deeper problem of homelessness.

“Until the real issue is addressed, nothing gets fixed. Taking away benches from the general public who enjoy sitting along the Ala Wai Canal is most certainly not the answer, but the easy button to quickly address an issue that homelessness has caused,” he said.

Others thought the new seats along the Ala Wai might serve their intended purpose.

“The new seats are OK. They prevent people from sleeping yet at the same time they are big enough for someone out on a walk to sit down and enjoy a cup of coffee,” said Robert Boyd.

Boyd was fishing for Samoan crabs along the Ala Wai when I spoke with him on Sunday.

Just a few blocks down from where Boyd was crabbing I saw a homeless man who already had found a way to transform one of the small green seats into his own residence. He packed belongings into the perforated metal seat made for two people, standing beside it to guard his bicycle, hiking boots, bedding and other possessions.

In 2014, the city began putting dividers on the benches at some of Oahu’s nearly 4,000 bus stops to keep homeless sleepers from stretching out on them.

But many homeless people then began to sleep instead on the ground around the benches.

The city also replaced benches at some bus stops with concrete stools that can accommodate only a single person.

Oahu Transit Services general manager Roger Morton in an interview described such anti-homeless features at bus stops as “lie-down-unfriendly-furniture.”

The problem is the backless, hard concrete “furniture” is unfriendly not only to homeless sleepers but also to non-homeless bus riders, including some older people with health problems.

Hostile architecture also can be created by entirely taking away places to sit like Mayor Jeremy Harris did in 2002 when his administration removed all the public benches on the Fort Street Mall.

The goal was to get rid of homeless people and drug dealers who were starting to dominate the downtown shopping area.

Chinatown community advocate Lynne Matusow, then the president of the Downtown Neighborhood Board, criticized the action in a 2004 interview: “We are not going to get rid of the homeless people. You just get rid of all the amenities for all the law-abiding people.”

Matusow said Sunday in a phone conservation that 18 years later, homeless people and criminals are still frightening pedestrians in the area.

“The bench removal actions were aimed at druggies, drunks and the homeless people, but they found other places to sleep nearby and law-abiding citizens still are left with no benches to sit on to eat their lunches, relax, talk and enjoy themselves,” she said.

The city also removed benches and tables in the Waikiki beach pavilions fronting Kuhio Beach to curtail homeless people who started turning the pavilions into their oceanfront bedrooms.

Some of the pavilions have since been rented out to commercial businesses and only one is open to the public just for sitting, but it has no tables and only a few benches.

Hostile architecture has been around for a long time. According to an entry in Wikipedia, anti-urination devices were incorporated into the walls in cities in 19th century England.

In Honolulu’s Chinatown, exclusionary design is evident in the fenced off doorways designed to deter homeless people from using the private doorsteps as urinals or sleeping areas.

Also, in Chinatown I saw a doorstep with cones placed on it hoping to prevent anyone from seeing it as a resting place.

British artist Stuart Semple created a website to launch an international movement hoping to end what he calls such “designs against humanity.”

The website says its goal is to raise awareness about hostile design, get people to openly decry it and encourage urban planners to create more rather than less welcoming public space for everyone.

Public benches and tables now removed need to be reinstalled for the public to enjoy once again.

The answer to homelessness is more complicated than removing potential sleeping places — the answer is doing a better job of addressing the reasons people are unsheltered in the first place and enforcing laws and ordinances that make it unlawful for them to turn public property into their bedrooms.