It would be a mistake to view Portland’s shortage of homeless shelter beds as just a shortage of beds — or just a problem for Portland. The city is dealing with failure to address serious underlying problems in our economy and social service safety net that won’t be solved with more capacity at the homeless shelter.

Recently, the city has been overwhelmed with people overflowing the city’s homeless shelter and also an emergency overflow space at the Preble Street Resource Center. City staff members have been forced to make more room in an office, where most nights shelter-seekers sleep sitting in chairs.

This is not just a typical seasonal influx. Numbers tend to be higher in the summer. But the more than 400 people a night lining up for a place to sleep is the largest group of shelter-seekers in Portland since the city began keeping track of numbers in 1987.

Several forces are working together to increase the size of the homeless population, and they are more than social service providers or the city can combat on their own.

The demand for shelter beds comes at the same time as other signs indicate the economy is not recovering fast enough. Maine saw its unemployment rate grow again last month, increasing by half a percentage point since the beginning of the year, growing from 7 percent to 7.5 percent. At the same time, state tax officials report that tax collections are below projections, both for income and sales tax revenues, indicating a lack of commercial activity.

While that alone helps explain the increase in demand at the shelter, homelessness is a much more complicated problem than a simple response to economic indicators.

The state’s failure to provide adequate community mental health care services is also contributing to the problem. So is the lack of drug treatment programs. Neither is a city responsibility, but the city is left dealing with the consequences when the state fails to meet its responsibilities. Providing a night’s shelter is better than nothing, but it does not address any of the underlying problems.

Portland officials know what they could do to address underlying causes because they did it for two years. The Homeless Prevention, Rapid Rehousing Program deployed social workers and rent assistance funds to get homeless people off the streets and connected with the services they needed to stay off. The program worked until the federal stimulus funds that supported it ran out last November.

Providing shelter to people who need it is the right thing to do, and the city should be commended for taking its responsibility seriously.

But unless the state and federal governments take their responsibilities as seriously and make a better effort to address the causes of homelessness, this will be a losing battle. And that won’t be a problem for Portland alone.