Study examines global warming’s effect on temperate rainforests

We have heard a lot about global warming and its impact on tropical rainforests – however, this phenomenon can have dramatic effects on temperate rainforests as well. A recent study published in BioScience examined the repercussions of glacier melt in temperate rainforest ecosystems, and how climate change will drive the future of nearshore aquatic ecology.

Glacier mass loss and temperate coastal chemistry
Shad O'Neel et al, the authors of the study, chose to look at the Pacific Coastal Temperate Rainforest, which lies along the western coast of North America from Kodiak Island, Alaska, to Northern California and stretches for 4,000 kilometers. Although many of the similar temperate rainforests have been lost in Europe and other areas due to overharvesting, the PCTR is remarkably intact and one of the "least anthropogenically modified ecosystems of Earth," according to study authors.

"One major area of concern is extremely short glacier-to-ocean stream length."

The life here is just as impressive as the ecosystem's longevity. Throughout the PCTR, there are old-growth forests, wild fish habitats and unique glaciers and ice fields. Many of the communities near the PCTR also thrive off of the tourism these natural attractions bring.

However, scientists agree that if climate change patterns continue, the PCTR will become wetter with less snow, which will not only harm the financial health of the the communities near the PCTR, but also the physical and chemical hydrology in the water. In fact, the researchers wrote in the study that climate change is currently having more of an ecological impact on the northern regions of the PCTR specifically, even more so than regional climate events like El Nino, the Pacific Decadal Oscillation and the Arctic Oscillation.

About the northern PCTR
It's important to understand the state of the northern PCTR to see how this will affect organisms downstream. Glacial coverage accounts for around 16 percent of this region, with 141 lake-terminating glaciers and 49 tidewater glaciers. Needless to say, with such a large amount of glacial coverage, the potentially devastating effects of glacial melt due to climate change is wide-reaching and potentially harmful to local wildlife.

In fact, according to Glacier Hub, the glacial melt in this area is vitally important, especially since changes to the aquatic environment in this setting can have a direct impact on primary freshwater sources to the Bering Sea. Glacier runoff could also present changes to plankton and benthic macroinvertebrate community structure as well as regional species diversity and coastal oceanography.

However, one major area of concern for scientists is the potential repercussions of extremely short glacier-to-ocean stream length throughout the PCTR. These areas allow quick delivery of riverine substances to nearby estuaries and fjords, affecting the entire ecosystem as a whole. This freshwater runoff supply is crucial for several reasons, but the biggest concern for O'Neel and the other scientists involved with the study is the organic matter that makes its way through these waterways and into nearshore environments. Mainly, scientists fear that melting glaciers will also usher many contaminants into these diverse nearshore settings, including fossil fuel combustion byproducts and mercury.

Glacial melt impacts many freshwater species downstream. Glacial melt impacts many freshwater species downstream.

Glacial melt in the PCTR and species diversity
Historically, an increase in glacial runoff results in more species diversity as well as species turnover. According to study authors:

"Streams with moderate basin ice cover (5 percent – 30 percent) tend to have the highest macroinvertebrate taxonomic diversity, although macroinvertebrate abundance is generally low in these watersheds."

Changes to the water flow also impact fjord species that are popular to wildlife tourism industries, sockeye salmon in particular. Additionally, these glaciers serve as important protection for several North American predator species, harbor seals and seabirds, affecting the entire ecosystem of an ecologically important region.

Moreover, the rapid environmental changes taking place in the area will likely influence a lot of decisions both regionally and economically as glacial melt continues to impact this thriving tourist region. As the researchers conclude: 

"A holistic scientific approach should be undertaken to begin to resolve these uncertainties in ways that maximize utility to the resource management community and allow efficient and informed decisionmaking in an era of rapid ecosystem change."

Conducting bioassessment and biodiversity surveys in the areas near the PCTR could offer valuable insight into how glacial melt will impact the aquatic macroinvertebrate community structure of local waterbodies in the years to come. Because a lot is at stake for this region both environmentally and economically, companies that provide consulting services and taxonomic laboratory services could contribute significantly to understanding the impact of climate change on this one-of-a-kind temperate rainforest.