ORONO – Loggers, biologists and silviculturists gathered at the University of Maine on Thursday to discuss one of the hottest questions in forestry today: How do you identify a healthy forest?

In recent years, a worldwide focus on forest biodiversity – the variety and density of life – has expanded the already complex world of forestry from trees to every creature great and small that inhabits woodlands.

Commercial forest certification programs require a commitment to biodiversity and increasingly, state and federal governments are doing the same. In fact, Maine’s Forest Service, as directed by a 1998 law, will publish its list of indicators for forest biodiversity by the end of the year.

“It’s a sea change in the forest management community … it’s not if we’re going to do it, it’s how we’re going to do it,” said Mike Thompson, who has been a member of certification teams through his work for a forestry consulting firm in Topsham.

Manomet Center for Conservation Sciences brought together about 50 people for Thursday’s discussion of measuring biodiversity, with speakers who addressed the issue on a local, state and international level.

Manomet, a nonprofit conservation group based in Brunswick, has spent the last year researching indicators used to measure biodiversity.

The complexity of biodiversity makes the issue particularly challenging for policy-makers and forestland owners who haven’t studied ecology. The loss of an insignificant-seeming lichen or beetle could be crucial to the overall health of a forest. And, particularly in Maine, the details of forest ecology aren’t well-understood.

“The issue is clearly something that we need to pay attention to, even if the science is not exact,” said Donald Mansius, director of forest policy and management at the Maine Forest Service.

The morning’s keynote speaker, a Swedish research scientist named Lena Gustafsson, shared her nation’s approach, which relies heavily on the habits of particular species to determine whether a logged forest remains a healthy, functioning habitat.

More than 2,000 Scandinavian forest species have been studied, and land with a high biodiversity value must, by law, be protected. Sweden is ahead of Maine in many ways, but balancing forestry and ecology remains a struggle. The country is facing future timber shortages because of the emphasis on preservation, Gustafsson said.

Here in Maine, forestry debates traditionally have focused more on the means of harvest than on what’s left behind. But biodiversity requires a different approach.

Just because a piece of land isn’t clear-cut doesn’t mean it will be a healthy habitat. For example, most loggers leave a few trees standing in a cutover area to retain some wildlife habitat, but a single tall tree with no forest around it doesn’t do much to improve the biodiversity.

And in some cases, clear-cutting an area and using replanting and herbicides to re-establish a native forest can be tremendously beneficial.

“Forest sustainability is an abstract concept. It’s more than answering the simple question: Are we cutting more than we’re growing?” Mansius said.

The ultimate goal of biodiversity efforts is to retain as natural a forest system as possible – a much harder task for some large logging operations than for small woodlot owners.

“The more you alter the habitat, the more you really have to be on top of your game with biodiversity,” Thompson said.

The Maine Forest Service’s list will set statewide goals for Maine’s forestland, in hopes of creating incentives for preserving biodiversity without new regulations, Mansius said.

The state list of statewide biodiversity indicators is expected to include such items as the number and size of dead trees, the tree age and species ratios, the use of protected areas to close some valuable habitats to harvesting, the amount of land that has not been divided by roads and development, and the presence of forest wetlands, he said.

Through intense negotiations, Maine has kept its list short and “doable,” in hopes of encouraging foresters to comply without additional and costly regulations, Mansius said.

“There’s going to be a compromise,” Thompson said. “We don’t expect perfection from any one landowner, and we don’t expect a single solution either.”