Climate change effects on Michigan's fisheries
Climate, the long-term pattern of temperature and precipitation, varies greatly from the Upper Peninsula to southern Michigan. This variation in climate creates differences in water temperatures and stream flows across the state which in turn influences where different fish species live, how well they reproduce and grow, and the types of fisheries we see around the state.
For example, walleye reproduction is better in northern lakes because those fish experience longer winters and cooler summers which favor this species. Therefore, it's critical to understand the importance of climate on Michigan lakes and streams and their fisheries, and how future changes in climate may affect these resources.
"Our climate is clearly changing," said Kevin Wehrly, a DNR-Fisheries Division research biologist from the Institute for Fisheries Research. "The earth's temperature increased about 1.5 degrees Fahrenheit over the 20th century. We are experiencing hotter summers and shorter winters. Ten of the hottest summers have occurred since about 2000, and 2016 was recently named the warmest year in recorded history."
Climate change isn't just changes in temperature, but also changes in precipitation and an increase in intense storm events.
Changes of just a few degrees may seem trivial, but they have important effects. There are some great examples from the agriculture industry. Take for example the plant hardiness maps produced by the U.S. Department of Agriculture (USDA) which have now been updated twice in the past 26 years to reflect changes in our climate. Growing conditions in Michigan today look more like those experienced in Kentucky back in 1990.
"Another example involves the loss of Michigan fruit tree crops in recent years," explained Wehrly. "We are experiencing earlier spring warm ups which cause fruit trees to bloom earlier. However, when an early spring warm-up occurs before the date of the last frost (an event that has become more common), a freeze will destroy the flowers and wipe out the fruit crop for that year."
When you see examples such as these, there's no denying the fact our climate is changing and we need to pay attention.
What about future climate change? There is overwhelming agreement by the scientific community that our climate is and will continue to change. Summers will get warmer, winters will get shorter, and Michigan will experience more precipitation and an increase in the intensity and number of spring rain events. By mid-century, Michigan's climate may feel more like Ohio and Kentucky and by the end of this century; our climate will be closer to the current Missouri and Arkansas climate.
It is uncertain what future climate change will mean for Michigan's world class fisheries. To allow better planning for the future, the DNR's Fisheries Division has started a program to evaluate how lakes, streams and their associated fish communities will respond to warming temperatures and increasing precipitation. To do this, Fisheries Division is building models that explain current conditions and then examines likely future climate projections to forecast changes. Currently, staff are evaluating about a dozen different climate projections which provide a range of likely scenarios.
"Our preliminary results suggest that under all future climate scenarios there are clear winners and losers," Wehrly said. "Warmwater species such as largemouth bass, bluegill and other panfish are the winners and will see an increase in habitat in Michigan. The losers are coolwater species such as walleye and coldwater species such as trout. Fewer stream miles and lakes are expected to support these species under the projected future climate. Our findings match the results found from similar analyses around the country and our observations are in close agreement with observations from fisheries scientists in Wisconsin and Minnesota."
The results of this program will help the DNR-Fisheries Division identify the aquatic species and waterbodies sensitive to climate change. This information will allow the DNR to protect places that are resilient and shift management to more appropriate species as habitat suitability changes in the future. For example, restoring currently reduced tree cover along coldwater streams that are sensitive to climate change may reduce the rate at which those systems warm up and allow the maintenance of high quality trout populations further into the future.
Another key factor is managing public expectations about our aquatic systems. The DNR needs climate change modeling information to inform anglers and policy makers that Michigan's lakes and streams are changing and we may need to change the way we manage them in the future. The DNR is working to refine its models using the best available information to ensure predictions are realistic and scientifically sound. Increasing monitoring of fish populations and water temperatures around the state will help to better understand how current and future climate influences Michigan's lake and stream fisheries.