A Zillow senior economist found that Amazon's second headquarters, known as HQ2, could add more than 800 homeless residents to New York City and more than a dozen to Washington, DC on an annual basis.

Both cities already suffer from some of the worst homelessness crises in the country.

Rising homelessness in Seattle — the site of Amazon's current headquarters — could presage what's to come in each HQ2 site.

Amazon's HQ2 announcement has ignited a war of words between local politicians, residents, and media outlets. While many have touted the tech giant's move to New York City and the Washington, DC metro as a way to boost economic development, others are concerned about the impact of thousands of new residents and two massive headquarters.

As Amazon begins its slow takeover of Long Island City, Queens, and National Landing (the site of three urban districts in Northern Virginia), the company will introduce around 25,000 new employees to each area over the course of ten years.

Read more: New Yorkers are making lots of doomsday predictions about Amazon’s HQ2. Here are all the things that could make it a disaster.

In neighborhoods that are already experiencing rising rents and crowded public transit, this could give way to further issues of congestion and affordability.

It could also have serious repercussions for homelessness in both New York and DC.

A Zillow senior economist recently found that Amazon's HQ2 could introduce 830 new homeless residents to New York City and 14 homeless residents to DC on an annual basis.

That's a small number compared to the existing crises, but it could represent a long-term challenge for both cities, which already struggle to accommodate their homeless populations.

New York City currently has around 77,000 homeless residents, the most of any city in the United States. But DC has a greater number of homeless residents relative to its population size. With around 7,500 homeless residents, DC outranks every other city in terms of its overall share.

The addition of more than a dozen homeless residents per year could put pressure on individual neighborhoods. As of earlier this year, Arlington County — home to two of the three National Landing districts — had a reported 221 homeless residents. The addition of 14 people would represent a more than 6% increase in the county's homeless population.

Though it's possible that the Amazon effect will be less dramatic, the company's impact in Seattle — the site of its current headquarters — could presage what's to come.

In the last ten years, the number of Amazon employees in Seattle's South Lake Union neighborhood has risen to more than 45,000. Since 2014, the city has seen its homeless count increase each year by 9%.

Amazon's response to the crisis has been somewhat unsteady. In 2016, Jeff Bezos donated $1 million to Mary's Place, a homeless shelter near the current Seattle headquarters. But the company also opposed a tax on large companies in Seattle that would have set aside $47 million per year for affordable housing projects and homeless services.

Amazon did not immediately respond to a request for comment on whether HQ2 might cause an uptick in homelessness in Long Island City or Northern Virginia. In June, the company said repealing the Seattle homeless tax was "the right decision for the region's economic prosperity."