Hard hats and construction vehicles have become frequent visitors to Tulsa's downtown as the core of the city continues to transform. But with more development downtown picking up, more trees are coming down, leaving some local organizations and residents stumped. And some say this lack of green downtown is becoming a challenge on an ongoing basis.

"It is more disappointing in some ways because we have much fewer ways to incorporate green space downtown," said Anna America, executive director for Up With Trees. "We have less room for error."

In some instances, trees get the chop because they outgrow the area where they are planted, resulting in branches growing into power lines or roots growing into buildings, roadways and sidewalks, buckling the concrete. Other times, unhealthy trees pose a safety hazard for those who walk or drive below, America said.

"In general, there are times when either because of disease or because of the most common case -- trees are planted in the wrong place -- trees end up being cut down," America said. "You see that particularly in urban situations. It's easier to take a tree out than trying to solve the problem."

But with few opportunities to incorporate new green spaces in areas already developed downtown, a change in attitude is in order, America said.

"In general, we'd like to see more people think about the alternatives," she said. "Is there a way to accommodate the tree? There are some places where they are redoing a street and will literally move a curb to go around a tree in the neighborhood. That doesn't tend to be the way we approach things here, either privately or publicly."

One development site has left a line of tree stumps along the streets of downtown, resulting in phone calls to the Up With Trees organization from concerned Tulsans. As the First Presbyterian Church began constructing 55,000 square feet in additional space, more than 20 trees that had been a part of downtown for decades faced the ax last month.

But the move to cut down the trees was one made out of necessity for the more than $30 million expansion project, said Steve Caldwell, the church's director of operations.

"We had to consider their age, health and likelihood of surviving the work on new sidewalks, drives, buildings and parking lots," he said. "Some of the old trees had raised sidewalks, causing trip hazards in places."

A number of the trees that ran along the roadways on the east and south side of the block also had to be cut down to make way for new driveways into the campus. Other trees were knocked down in a parking lot for a newly constructed administration building and courtyard, Caldwell said. Trees on the north side of the block had already been lost to disease and wind damage throughout the past few years.

Even though, often times, trees chosen to be planted in urban areas are selected because of their resilience, America said even the sturdiest trees sometimes do not do well in city soil and urban elements from vehicles and traffic.

Many of the trees had been planted in sections of the sidewalk around the block, but the trees were not part of public property, said Mary Coley, city of Tulsa's communication officer.

Although public right-of-way improvements include anything from sidewalks to sewer lines, "what many do not understand is that in Tulsa, property owners are responsible for maintenance and upkeep of the landscape, lawns and trees on (a) right-of-way that directly abuts their private property," said Steve Carr, the city of Tulsa's senior planner and project coordinator.

The church plans on planting new trees after construction is completed in early 2012, he said. Many of these trees will be planted in the same spots where the old trees were cut down near sidewalks on the north, south and east side of the block.

"The overall project, landscaping included, is such an enhancement," Caldwell said. "The loss of the older trees will simply be forgotten."

But these older trees in an area like downtown often help residents in ways they might not even realize. April Hastings, outreach and volunteer coordinator for Up With Trees, said these larger trees help to soak up standing water and alleviate scorching temperatures during the summer months.

America said she understands that sometimes there are few ways to stop the chop with a need to comply with ADA regulations when sidewalks buckle from root growth and when diseased trees pose safety hazards. In some instances, sidewalks should be left with a slight slope from root growth if it does not prevent mobility. However, as development envelops downtown, America said a tree's best chance at survival depends on developers and landscapers today.

"That's a huge problem for trees, in general, is that people don't tend to think ... where that tree is going to be in maturity," she said. "That is one of the most important things for tree survival is the right place for the right tree. Really think about what is appropriate for (the area) 20 to 30 years down the road."

America said to try to plant trees away from sidewalks and buildings, giving them room to grow. If there is not sufficient space, look at different kinds of species of trees to determine what will be best for that area in the future. Up With Trees also provides a list of city-approved trees organized by size and species giving landscapers an idea on what can be planted where. But companies should generally leave landscaping up to the professionals, she said.

"Businesses in downtown should definitely not be going to Home Depot and sticking trees in the ground," she said. "They need to find a landscape architect ... who knows enough about trees that plans for that tree to be healthy a couple of decades down the road."

Although the First Presbyterian Church has not awarded its landscaping contract to a company yet, Caldwell said the company chosen will be one that focuses on tree selection and will ensure mature trees will not encroach on the sidewalks.

Soon, more green will be seen in downtown Tulsa, Carr said. The Downtown Coordinating Council recently chose the landscape architect company Howell & Vancuren to develop a tree planting plan for downtown Tulsa. This same firm has completed streetscape and landscape projects inside the IDL, he said.

Tulsans will also be seeing more green if the Downtown Area Master Plan is adopted, Carr said. The plan includes a proposal to create green spaces on private and public land throughout downtown, including parks in the Brady Arts District, near the Oklahoma Jazz Hall of Fame, near Tulsa Community College's Metro Campus and in the East Village.

Up With Trees is also looking at ways to re-green Oklahoma. To prevent tree demolition from branching out into the future, Up With Trees has been experimenting with an innovative way to plant trees in newly developed areas. At the recently constructed Village on Main in Jenks, the organization planted trees surrounded by a box to help encourage roots to grow down rather than out, helping to alleviate damage on sidewalks and roadways, America said.

"Beyond the beauty, there is a huge environmental and economic benefit trees bring to a downtown and to a city," she said. "We need to recognize they have value."