Last Tuesday the Massachusetts Fisheries and Wildlife Board held its July meeting via Zoom. In it there was a presentation by Dr. Rebecca M. Quinones, the MassWildlife Rivers and Stream Project Leader who is an expert in aquatic biology and climate change. Much of the information used in her presentation was derived from an article in the June issue of Frontiers in Ecology and the Environment, which she co-authored.
The focus of her presentation was to help the Board understand and address the impact of climate change in Massachusetts and how it impacts streams, in particular cold-water habitat, and how those changes can be reflected by fish responses.
Ultimately, the goal is to identify cold- water climate change refugia (areas where conditions can enable a species to survive after extinction in surrounding areas). She noted that it is necessary to think about these areas in order to develop specific restoration and land protection actions that would continue to provide good habitat in the future.
Generally, in the Northeast, there has been a 1 ½ degree Fahrenheit (F) temperature increase from 1970 to 2005. The changes in temperature have some differences seasonally so, for instance, scientists know that winter temperatures are warming faster and in that same time frame they know that temperatures have increased about 4 degrees F. That has implications for precipitation that we are seeing across the state, particularly the range of snow ratios. We are seeing much more rain and that has resulted in a 7% loss of snow and a 16% decrease in snow pack in March and April and that has heat implications for the hydrology. We are now seeing more higher peak stream flows in the spring, about 2 weeks earlier than historically. On one side of the spectrum we are seeing peak flows increase, but on the other side of the spectrum droughts are becoming more frequent and droughts that last a few months have become more frequent over the decade.
There are studies that project that the Northeast is feeling the impacts a lot faster than other parts of the world. Studies show that a typical degree increase in Celsius (C) will be likely coming our way by 2040, in comparison, in the continental US, it will probably occur sometime in the mid 2040’s. That still is much earlier than we would see it happen in the globe as a whole which is likely to happen around 2060.
It is anticipated that conditions in MA will be more like the southern states by 2099. The weather here is likely going to be similar to what is being seen in South Carolina now. So, when scientists start to think about cold water climate change refugia and see what it looks like in SC, then they might have an idea of what kind of a characteristic we can expect. The distribution of cold-water species will shrink to by 2099.
The changes they are expecting in cold water streams that stay pretty much intact, will remain fully functioning cold water streams. But we may have other systems that may transition and become completely transformed with different types of habitat available to them.
If you are a fish, you will have only 3 options – stay in the habitat you are in and try to adapt to the changes, move to more suitable habitat if there are no barriers (dams, culverts, etc.) and you have the capacity to do that, or you can stay in place and die. We are seeing those responses already in all the cold-water fishes. In several fish species in the northeast, in some areas we are seeing that trout can continue to do well. They are able to deal with warmer conditions, but not so warm that it will impact their ability to assimilate foraging enabling them to grow.
In some areas we are seeing trout grow much faster in warmer conditions, but if we exceed the tolerance of the temperature that they can thrive in, the brook trout actually decrease in survival. It becomes much more obvious in larger age classes particularly under drought conditions. Because of the increased frequency of the droughts, we might see survival decrease across the state. We are also seeing changes to earlier upper migration which causes earlier spawning.
So, if we are seeing changes in habitat, there is the likelihood that we will see changes in the assemblage. In some habitats, you may see the species change from trout to warm water species.
Dr. Quinones is hoping that we move forward to where we are thinking about the exposure of species to climate change, their sensitivity and adaptability capacity (the 3 vulnerability elements where we think about climate change impact).
There are landscape characteristics that define what residual habitat could be and could act as climate change refugia. Refugia are not meant to be static. They are still going to be impacted by climate change but its impact will be felt at a much lower pace.
For cold water climate change refugia, you could look at elevation. Habitats in higher elevations tend to be colder and might stay colder for longer periods of time. Likewise, you have cold-water from deep snow, and snow-packs can mitigate warm water temperatures. Likewise, being in a valley having a lot of canopy cover can increase the amount of shading, protect the streams from solar radiation and keep them cooler.
There are other characteristics such as being on north facing slopes, ground water which can give some source of cold water and deep lakes which stratify with cold water bottoms which provide cold water habitat.
MassWildlife has put together a team which has been thinking about temperate change, on brook trout specifically, for many years. Brook trout have been used as an emblematic species in the state, representing the suite of cold-water species. They are already working with models trying to determine how the species might survive into the future.
They have charts and maps enabling them to see the range of the brook trout in MA. Surveys have been conducted in MA fisheries from year 2000 and a data base, especially on larger rivers, has been created. These models give them opportunity to think about climate change problems.
In the predicted 2-degree C increase in July temperatures by 2040, you might see a 42% decrease in streams that could support brook trout in summer. Of course, there might be small pockets of cold water, while some areas might become warmer quicker than others.
A 4- degree C increase in temps which may occur by the 2070’s indicates another 28% decrease in the amount of cold waters available in July. If a 6 degree C increase in temperatures, which is projected by 2099, occurs there will be another 25 % decrease in cold water streams that are supporting brook trout in summer. By 2099 there could very well be a 77% drop in the cold-water streams available for habitat for brook trout.
The projections indicate that perhaps some of the cold-water streams located primarily in north western MA could be cold-water climate change refugia. Even with a 6 degree C temperature increase, they could still provide cold water habitat for brook trout. The headwater streams will provide cold water habitat but there are also high risks of becoming dry during a fluctuation of flow. High temps affect the high parts of the watershed as well as the low.
After Dr. Quinones’ presentation, the F&W Board conducted discussions regarding climate change. DFW Directors Mark Tisa and other Division aquatic biologists assured them that they recognize the importance of cold-water streams and have spent more than 20 years finding out where they are. In their land acquisition decisions, they are high on their radar screen and give priority to lands with cold water streams.
Dr. Quinones noted that there are great trout habitat areas today that are likely not going to be in the future. Those are areas where restoration would be really important. Groups like Trout Unlimited have been doing a lot of restoration on the ground and these are areas where she can see them moving work forward.