Saturday, April 20, 2024
April 20, 2024

Watershed work aims to avoid ‘catastrophic’ wildfire, protect drinking water  

A collaboration between climate scientists and Salt Spring’s largest water utility is yielding data — and a plan to improve both forest health and drinking water security for the island.  

Trustees of the North Salt Spring Waterworks District (NSSWD) heard an update from Transition Salt Spring’s Climate Adaptation Research Lab (CARL) scientist Ruth Waldick at their monthly meeting Thursday, Feb. 23, covering information collected upon — and current plans for — the Maxwell Lake Watershed.   

NSSWD withdraws and treats water from Maxwell and St. Mary lakes, and has been partnered with CARL since early discussions with the water district’s staff and trustees in 2021.  

“At that time, I remember clearly,” said Waldick. “Vaughn [Figueira, NSSWD’s operations manager] said there were issues with sedimentation and nutrients — phosphorus in particular, we wanted to know where the sources were — and about the risk of fire.”  

So with data from public aerial imaging sources — and from small armies of volunteer scientists, often graduate students recruited for some on-the-ground learning — Waldick and CARL started cataloguing and mapping. The result is a living, often-updated picture — an increasingly precise understanding of the nature of the forest at every point on the watershed.   

An extensive water sampling project has been critical to planning as well; a healthy forest surrounding a lake has an outsized impact on improving water quality. The hydrology phrase is “residence time” — the longer it takes for that fallen raindrop to reach the lake, the less sediment it carries with it. Drained wetlands and a criss-crossing network of planned or unintentional roads, ditches and drains has led to a lot of fast, sediment-filled water coursing down hillsides — a less optimal situation for the trees, according to Waldick.  

“The faster the water moves through, the quicker the ground dries, adding another element of stress on the trees,” said Waldick. “If we want to have robust, healthy trees, we need to make sure they have as much moisture as long as possible.”  

Looking across the map, you can see places where the trees are taller, or older, spots where large swaths of fallen timber dominate the ground cover, or sections where the underbrush is stunted by lack of light, where tall, nearly branchless trees have created a high canopy far above the forest floor.  

The latter is cause for particular concern; there are many kinds of forest fires, of course, but few move as quickly as the kind that leap from one treetop to the next. So-called “crown fires” spread rapidly, largely due to their height. Well-exposed to winds, the flames and sparks jump between the tight and often interconnected branches uncontrollably.      

On the map, dark red patches show these areas around the lake — Waldick showed photos of tall trees that looked like hydro poles, except for high, bushy branches blocking out the sun. There are some breaks between the high-ignition-risk areas — along high-voltage power lines, for example, or some stands of Garry Oak that naturally keep their distance from one another — but not nearly enough.  

By way of comparison, within Mount Maxwell Provincial Park — where more natural growth has created distinct and separated patterns of disconnected canopies — there’s less danger of one tree igniting the next. That’s the model, according to Waldick — a forest that protects itself. In the watershed, it’s going to need some help in the form of forest modification.  

“What we want to do is create more ‘patchiness’ over time,” said Waldick. “It introduces some fire resistance that is natural to the forest, and reduces the potential for catastrophic spread of fire. With our thinning we’ll open gaps, which will also let more light in.”  

Left on their own, these high-canopy forests tend to eventually be out-competed by their neighbours; they are, arguably, dying. But waiting for the forest to heal itself means accepting that, sometimes, the natural process chooses fire — the worst outcome for nearby water users.  

A large wildfire around a drinking-water lake — even if it miraculously spared the utility’s equipment — would precipitate years of water too full of contaminants to effectively treat for drinking; when the vegetation holding soil in place burns, that soil flows downhill right alongside ash from the fire, contaminating the water and often contributing to harmful algae blooms.   

More than half of Salt Spring gets its drinking water from lakes and streams.  

Waldick said specifics vary, but the data show Salt Spring is getting more of our rain in the winter, and less of it in the summer — a shift that’s predicted to be about 20 to 25 per cent over the next few decades. The more data that can be collected, the more accurate these models become — so the CARL team has set up 10 long-term monitoring sites at several points on the watershed, including some on private land.  

“We have a commitment from Foxglove Farm, and sites on Greg Johnson’s property to the east of the watersheds,” said Waldick, “so we can understand the variety of things going on in the soils, the different forest types, why some areas look better than others.”  

The good news: more accurate data means CARL can target parts of the forest that really needs the work, and are more at more risk than others. Instead of changing the whole watershed, they could prioritize work, in manageable chunks.  

“We want to focus on areas around trails,” said Waldick, “because that is where people will be — and people start fires.”  

From there they analyzed fuel loads — the things that would take a careless spark and turn it into a disaster. The plan of attack begins with controlled thinning, and moves into some cutting-edge forest restoration and fuel management practices, working with graduate students — like bundling smaller downed timber and arranging it to mimic a fallen old-growth tree in how it holds moisture, accelerating decomposition and encouraging seedlings.  

All that starts to restore the soils, said Waldick. “And when we open those patches, the trees get more light, they’ll grow bigger, they’ll get to the ‘old growth’ stage faster. We get more understory that is fire resistant, instead of just logs on the ground.”  

Despite utilizing notoriously affordable grad student labour — and some grants from sources like Environment and Climate Change Canada, and local sources like Transition Salt Spring and NSSWD itself — securing funding is ongoing work, according to Waldick. One idea to augment extant and incoming grant money has been to raise funds selling off material harvested from the thinning work — think of a solid-sawn heavy timber beam, and a homeowner knowing it exists specifically because of watershed protection and forest restoration.  

Waldick is optimistic; grassroots support, particularly from neighbouring properties and an academic world eager for an outdoor laboratory, has been significant. NSSWD trustee Chris Dixon agreed, joining the rest of the board in gratitude.  

“And it important that people on Salt Spring understand the issues up there, what you people are doing, and how utterly critical it is,” said Dixon. “We’re undoing decades of poor forestry management.”  

“I think we’ve been very successful so far,” said Waldick. “The volunteerism, the community contribution has been massive.”  

And, she added, from a climate change perspective, protecting the health of these forests may be “the single most important thing we can do on Salt Spring.”  

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