The Surprising Roles of Healthy Forest Landscapes
Even if you’re only loosely familiar with the Ruffed Grouse Society, you probably already know that healthy forests are very important for wildlife — and therefore to us. Diverse forest stands help provide the right mix of habitat for the wild birds and mammals that we love to watch and chase. But what role do these forests have beyond their value for wildlife conservation?
This Earth Day, many people all over the country are taking a moment to do something for our natural areas. Whether they’re cleaning up trash from parks or planting trees for the future, they are making a small but collectively measurable contribution. Similarly, natural resource managers across the country get the opportunity to make a difference throughout the year. I caught up with Jon Steigerwaldt, RGS Regional Biologist for Wisconsin, Minnesota, Illinois, and Iowa, to discuss the challenges and opportunities facing resource managers.
What is a Healthy Forest?
First, let’s lay the foundation for this discussion. What is a healthy forest and why does Ruffed Grouse Society promote it so heavily? A healthy forest is one that consists of a variety of age classes (e.g., young, immature, mature, old-growth) and species, which makes it reasonably able to withstand various threats to it. Threats to forest health are unfortunately abundant and include diseases, pests, invasive species, and extreme weather events, to name a few. Oak wilt, gypsy moths, emerald ash borer, buckthorn, and changes in precipitation can all wreak havoc on a forest ecosystem. But if the overall forest landscape is healthy, the effects from these threats will usually be smaller or more localized, and the forest can generally bounce back quickly. This is called resilience.
Historically speaking, many of our forested ecosystems evolved over thousands of years with some kind of regular disturbance shaping them, usually fire. However, in post-European settlement North America, we’ve done a lot to suppress these disturbances. By abruptly stopping these natural and human-caused processes, we’ve in many cases slammed the brakes on this evolutionary trajectory and given very little time for wildlife, forests, and ecosystems to adapt to change. Today, many disturbance-dependent species are in peril because of this sudden change to the way humans influence ecosystems. The fact remains that disturbance is important to many of these ecosystems.
Young forests are not only important to many wildlife species, including ruffed grouse and American woodcock, but they’re also very important for building that natural resilience. Timber harvests definitely create young forest structure quickly. But to simply clear-cut everything would be a very short-term gain and likely create an unhealthy forest landscape over time. Therefore, it’s time to place a greater emphasis on forest diversity.
How Important is Diversity?
Like the discussion above, diversity is the key to it all. Diverse forest stands help mitigate impacts to any one species when something threatens it (Duveneck et al. 2014). To use the ruffed grouse as another example, aspen forests provide great habitat. But without an understory of fruiting shrubs and hazel catkins, or a mature spruce to hide from predators, that pure stand of aspen is less attractive. Most, if not all, wildlife species have different needs throughout the year and throughout their lives. Having different tree, shrub, and herbaceous plant species, as well as varying age structures, helps to increase the overall value to wildlife.
Jon brought up a great point about the management implications of including diversity for adaptation. If we do a clear-cut and harvest a mature forest with 100 trees per acre, for example, we might get 20,000 stems re-sprouting in a few years. That is a tremendous increase in the sheer amount of genetic and species variability within that acre. Compared to the initial 100 trees, it’s far more likely that these new and diverse seedlings would have a few among them able to survive and persist through various threats (e.g., resistance to disease, better able to grow in certain conditions, etc.). On the other hand, if we rely on a monoculture of fewer mature trees, one pest or disease could come in and wipe them out.
Jon mentioned that this sets forth the concept of creating forest adaptation to current and future conditions. A good example of this adaptation concept would be regenerating/converting a red pine plantation with an active Heterobasidion root rot disease to a mixed stand of hardwoods and oaks with the help of a timber harvest. Hardwoods and oaks often occupy the understory of old pine plantations, so removing the mature diseased pine trees would release a diverse mixed stand of young trees. While the red pine plantation may have served its purpose by restoring an old agricultural field to a forested condition, active management can create adaptation to changing conditions by removing disease concerns and encouraging natural forest succession.
Healthy Forests and Climate Change
I hope it’s clear up to this point that healthy, diverse forests provide the highest quality habitat for many wildlife species. Destruction or loss of habitat is still one of the biggest negative impacts to many game birds across the nation. Nobody’s arguing that. But recall the question in the introduction: what else do healthy forests help with? Since it’s Earth Day, let’s just tackle this one head on.
Regardless of whatever you believe is causing it (natural cycles or manmade consequences), our climate is changing. An Intergovernmental Panel on Climate Change report from 2013 states, “Carbon dioxide concentrations have increased by 40 percent since pre-industrial times.” Average temperatures and precipitation levels are on the rise. Many agencies are already considering adaptive forest management strategies for climate change (Swanston et al. 2012; Handler et al. 2014). It’s the task of natural resource managers to adapt forestry practices to fit the current and expected future conditions given that information.
Here’s the interesting part: healthy, diverse forests can actually capture carbon, often referred to as carbon storage or carbon sequestration. Carbon sequestration is basically the process of carbon dioxide from the air being stored within the biomass of trees, shrubs, and grasses through the process of photosynthesis. This “carbon sink” is thought to help offset sources of carbon dioxide in the atmosphere. Different plant species and age classes also capture carbon at different rates, making diversity even more important (Bradford and Kastendick 2010). At first glance, it seems like a silver bullet solution — if we simply plant more trees and don’t harvest any, we will store more carbon and reduce the effects of climate change.
The problem is that humans are unlikely to suddenly stop using fossil fuels any time soon. Carbon dioxide levels are going to continue to trend upward. And while we have a general idea of how much carbon trees can store, there are just too many variables involved across forest ecosystems and regions to accurately measure it. But the other glaring issue is that if we suddenly left forests unmanaged, we would again be slamming on the brakes for many of our disturbance-dependent species. The impacts to forest health and resiliency, not to mention wildlife use and conservation, would likely be far more harmful in the end and exacerbate a possible ecological crisis. So where do we go from here?
As mentioned above, the best solution is to adapt the tools and processes we’re using. Adaptive forest management practices can be used to encourage diverse and healthy forest stands, which are more resilient to future effects from climate change. Holmes et al. (2014) and Millar et al. (2007) explain this with two concepts: adaptive management can be used to reduce the negative impacts of climate change (i.e., maintaining healthy forests and habitats), while mitigation refers to practices that actually influence climate change (i.e., carbon sequestration reducing atmospheric carbon dioxide).
Adaptive Management and Mitigation Practices
One management practice that Jon referenced is the role of fire in natural ecosystems. Most of us have heard that fire is important for prairie habitats, but many forests also evolved with a regular disturbance regime of human- and lightning-caused fires. Over the last hundred years and more, we’ve taken great care to reduce and extinguish wildfires. Unfortunately, that has led to a drastic increase in fuel (i.e., duff, standing snags, woody debris, etc.). When fires finally do occur, they burn at a higher intensity and tend to be more devastating. In some areas, climate change is expected to continue producing more precipitation, which would encourage additional vegetation growth to serve as a fuel source. In this example, restoring the natural process of more frequent, lower intensity prescribed fires may help restore the forest’s natural resilience. Although fires are destructive-looking and do release carbon dioxide to the atmosphere, the flush of new plant growth afterward also uses CO2 and sequesters it again.
Jon (who studied wildland fire ecology for his master’s degree) said that fire is not just a management tool to create resilient/adaptive forest ecosystems under a climate change model, but it’s a real-world solution to problems we face under an ever-expanding wildland urban interface. Wildland fire professionals generally agree that currently, a century’s worth of fire suppression, fuel load build up, and the growth of the wildland urban interface has had more profound effects on wildland firefighting than climate change. Fortunately, some states (Florida, for example) are great models for progressive prescribed fire/forest management in that wildland urban interface.
To the point above, another issue facing resource managers is how to tackle the existing threats to forest health today. For example, many forests ecosystems are suffering from diseases or invasive species, and managers or foresters don’t have the resources (e.g., funding, staff, etc.) to address it. These issues are causing problems today and will likely get worse in the future with the additional stress of climate change. It’s important to address these issues now to build resiliency into our forest landscapes for the future.
Navigating These Complex Issues
In the end, we don’t know exactly how climate change will affect our forests and wildlife because there are so many variables involved. Acting on one item in isolation may in fact produce greater negative effects elsewhere. But we do have a pretty good idea of the trajectory given the current trends and existing issues. Ultimately, management actions are developed by using the best available science at the time. In this case, having a healthy, diverse, forested landscape helps provide prime habitat for wildlife, promotes resilient ecosystems and functions, and offers enhanced carbon storage opportunities.
Talk about an Earth Day trifecta.