What ecological problems face coniferous forests today?

There are numerous threats that are specific to a particular type of tree or forest type, so these answers are very general. Forest fires have generally been suppressed over the last hundred years in the United States, and, as a result, are more prone to burn uncontrollably than ever before. Fires are a natural occurence, and in small quantities, improve habitat and wildlife diversity, but large-scale wildfires are less desirable in a natural and human settings. With a warming trend in Earth's climate at the moment, and with global economies moving wood materials and diseases on a global scale, insects and fungi that attack trees are spreading into new territories where trees do not have defenses against the attackers. For example, the blister rust (a fungus) has decimated whitebark pine trees, and the emerald ash borer and the gypsy moth are exotic pests wreaking havoc on North America's forests. Overuse of old-growth forests can also cause species to become endangered or extinct, such as the spotted owl. Old growth forest takes hundreds of years to form, and extensive logging can ensure that old growth forest never regrows.