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[ ♩ Intro ]
Wildfires are all over the news these days.
In North America, the number of forest fires has increased four-fold
in the last couple of decades,
with fires lasting longer and getting bigger every year.
And wildfires are an inconvenience and a danger for many creatures,
including us humans,
but they’re not always a bad thing for all animals.
One creature we might not expect wildfires to affect much at all are fish.
You know, since they live in water,
which is one place that fire tends to not do well.
But despite that, researchers have found
that wildfires can change the lives of our aquatic friends in a lot of ways.
In fact, we now know that even though wildfires have a lot of downsides
, some types of wildfires can be beneficial,
or even necessary, for their ecosystem to thrive.
Sure, when a wildfire happens, a pond
or stream doesn’t actually burn up.
But immediately after a fire, the quality of life in streams, lakes,
and rivers temporarily gets worse for the creatures that live there.
The water quality drops, and when the surrounding trees are burned badly enough to die off,
their roots are no longer there to hold the landscape in place,
which can cause it to become unstable.
And that often results in a large amount of debris falling into nearby bodies of water,
or being washed into them by the next big rainfall. Stuff like
burned trees, large boulders and mud.
This can also carry a lot of nutrients into the water,
which can trigger a massive algal bloom –
when the microscopic algae that live in the water all grow very quickly, all at once.
And at first , an algal bloom sounds like it would be great
for the ecosystem.
A lot of creatures use it as their primary source of food.
But the vast majority of the algae
that doesn’t get eaten eventually dies and sinks to the bottom
and as it decomposes, those decomposers consume a lot
if not all of the oxygen in the water.
Which is pretty bad news for the aquatic animals that need that oxygen to survive.
But there are some benefits.
In the long term, those trees and rocks can establish new habitats
for fish and other creatures in the water.
For example, increased numbers of logs, known as logjams,
can improve the quality of a stream or river by creating more hiding spots
for juvenile fish species.
All those logs and boulders can also help to create deeper pools of water,
where the water can be cooler than in the shallows.
And that’s great for fish species that need those cooler temperature ranges to survive.
Swimming around in warmer water temperatures can be very stressful for these fish.
It increases their energy expenditure and need for food,
which may or may not be available. So having places to chill out is vital.
Sometimes, though,
it’s not just nature that disturbs fish’s ecosystem during a wildfire.
Occasionally, humans get involved and try to contain or extinguish the flames.
When a fire needs to be brought under control,
firefighters will manually combat the spread by pouring dirt or water on the flames,
or by removing or wetting all of the underbrush before the wildfire gets there.
But when the fires become too big and too intense,
bigger fire suppression methods like chemical fire retardants have to be used.
These contain nitrogen-heavy compounds which, in high enough concentrations,
can be toxic to fish and other creatures that live in the water and create even more algal blooms.
Now, putting out wildfires before they cause all this ecological chaos
might sound like the obvious choice.
But researchers in the Pacific Northwest have found
that suppressing all wildfires can be counterproductive.
In the Wenatchee River basin, for example,
that approach is actually having a negative impact on some fish species in the area.
Their studies suggest that allowing little to no wildfire near streams
may be limiting habitat for salmon.
Without the upheaval that fire brings,
there are fewer logjams and boulders creating an ecosystem
that these creatures evolved to thrive in.
This has contributed to the decline of threatened fish species
like Chinook salmon and bull trout,
in combination with other factors like the fragmentation
and loss of their habitats.
The good news is that in 2015,
these researchers were able to model how these vulnerable fish populations
might recover if we humans changed up our fire-management strategy.
They modeled scenarios with different fire sizes and habitat connectivity.
And they predicted that in a future, warmer climate,
bull trout would fare better when some wildfires
were allowed to do their thing and create habitat variety,
including those colder pools of water they need to live.
Instead of us trying to completely prevent fires,
they argued that managing forests and allowing regular,
small burns would help support these vulnerable species in a warmer climate.
Here’s the sticking point, though.
Hot, high-intensity fires are becoming more common
thanks to the climate crisis.
And those are a way bigger problem than slower, lower-burning fires.
You see, low burning fires help clear out the underbrush in the landscape –
the stuff that otherwise becomes fuel for a bigger, more devastating fire.
They improve the diversity and richness of an ecosystem over time,
both on land and in the water,
whereas the high-intensity variety just demolishes everything in sight.
With high-intensity fires becoming more and more prevalent,
it looks like future fire management efforts need to literally fight fire with fire.
Research has shown that by starting controlled burns,
which mimic low-intensity wildfires,
forest managers can eliminate some of the fuel
for super intense fires capable of wiping out the entire forest ecosystem.
Smokey the Bear may tell has told us that only we can prevent wildfires.
But it’s worth keeping in mind that they are an important part of many ecosystems.
With proper management, fires can help ecosystems thrive.
Even in places where they can’t burn at all.
Today we talked about a pretty unexpected interaction in nature.
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