By David Mazerolle
Humans have always carried other organisms along on their travels, whether they be plants, animals, bacteria or viruses. Our recent mastery of ocean and air travel, however, has caused this mixing of the world’s biota to occur at an ever-increasing pace.
A substantial portion of New Brunswick’s wildlife is made up of relative newcomers, brought here intentionally or accidentally through human movements. In fact, over 30% (roughly 600!) of all plant species now found in the province didn’t exist here before European settlement. While most new arrivals don’t survive in our climate, some do become established and a small portion thrive in their new environment, becoming abundant and spreading into natural areas, predating on or out-competing native species, causing disease and becoming agents of change in our ecosystems. These invasive species can cause irreparable ecological damage and are considered one of the foremost threats to biodiversity worldwide.
Those of us who track the status of rare species and work to protect our natural heritage know that a considerable number of invasives have already had a profound impact in our region. There is no shortage of examples. Diseases caused by introduced fungi and insects, such as Dutch Elm Disease, Beech Bark Disease and Butternut Canker have changed the very composition of our forests. Glossy Buckthorn, a European shrub, is aggressively spreading in many counties, crowding out native woodland and wetland plant communities. European Green Crab is now established in many of our estuaries, where it feeds on shellfish and tears up the Eelgrass beds that provide shelter to numerous aquatic animals. Some particularly destructive species lie just beyond our borders. Such is the case for the Asian beetle Emerald Ash Borer, which will foreseeably spread to our province within a decade and by all indications may effectively eliminate all three of our native ash species.
As a driver of change in species distributions, direct human intervention is perhaps second only to climate change. Indeed, the spread of some invasives in our province, such as the European Green Crab and tunicates, is known to have been facilitated by warming trends. Many problematic species found in southern Quebec and New England have largely been kept at bay by our harsher winters. Ongoing warming of our air and water temperatures will undoubtedly allow some to settle here and spread. As such, we must keep an eye to the south in anticipation of future invaders.
At present, human-caused climate change is allowing native New England species to extend their ranges northward into our province, blurring the line between natural migration and exotic species invasions. Should these species be considered welcome additions to our flora and fauna? What of our commitment to the rare species and ecological communities that may be further imperiled by their arrival? Global warming is affecting profound changes in the composition and function of our ecosystems, which may require us to rethink our perception of the “natural” world. Addressing these questions will be key in our adaptation to climate change.
Faced with the enormity of this situation, it’s difficult to keep a positive outlook. But there is hope; as public awareness grows, federal and provincial agencies are increasing their commitment, environmental NGOs are becoming increasingly active in survey and control efforts, and new tools for detection and control are becoming available. On a local level, the recent revival of the NB Invasive Species Council is also a promising development.