Stories of Science—Brittany Harris


Brittany Harris is a fellow Ph.D. candidate at Florida International University in the Biology department and a good friend of mine. We met during an aquatic plants class that brought us to the Everglades and have been friends ever since. There has been a lot of concern lately with all of the fires making headlines. Since Brittany studies and works in a fire-dependent ecosystem, who better to sit down with and chat about them?

What’s your favorite flavor of ice cream?

I don’t really like ice cream probably coffee frozen yogurt. 

What is your dissertation about? The short version.

I study the effects of disturbances on pollination systems in islands. Disturbances—including natural (fire and hurricanes) and human-caused ones (mosquito spray). I study whole plant-pollinator communities. So I look at and measure pollinator and plant interactions like diversity of species, diversity of interactions, and who is interacting with whom. My study is along a gradient of fire history, with differences in severity, time since last fire, and frequency over the last 50 years.  

Where are you doing your work?

In the Pine Rocklands in the lower Florida Keys. The Pine Rockland ecosystem is a higher elevation pine forest with limestone outcroppings and very little soil. The keystone species in this ecosystem is the pine tree (Pinus eliotii). The landscape looks sparse but there’s a diverse herbaceous community. There’s over 400 native species that occur in this habitat and lots of endemic species that are found nowhere else in the world. Some of my favorites are Chamaecrista lineata var. keyensis (Big pine partridge pea), Byrsonima lucida (Locust berry), Leucothrinax morrisii (Key Thatch Palm), Linum arenicolum (sand flax). Pine Rockland is a globally endangered ecosystem with only 1–2% of what originally existed remaining in tact.

Pine Rockland habitat is a fire-dependent ecosystem, can you explain what this means?

Pine Rockland forests depend on fire every 5–15 years. Without fire for 15–20 years, the plant composition will eventually change from pines and the diverse understory to large hardwood trees. Leaves and branches of these large trees close in the canopy, the vegetation becomes denser, and leaf litter accumulates on the ground. The understory species need a lot of sunlight and low amounts of leaf litter for flowering, so without fire they don’t survive for long. Many of the plant species also need fire for their seeds to germinate. Bees not only need pollen and nectar from flowers to feed their young, but many of them need bare soil and dead wood to build their nests.

Hardwood hammock species essentially out compete the pines, making more leaf litter but not the kind that catches fire. Pine needles have resin (that’s what makes them smell nice when you crush them), which is very volatile, so pine needles catch fire very easily during lightning storms. Without the fire you end up with a one-way transition with little chance to revert to Pine Rockland. So not only is this habitat threatened by urbanization it’s also threatened by a lack of fire.

I have heard you mention the misinformation of Smokey the Bear, can you elaborate?

If we look at Pine Rockland as an example, fire has had a bad reputation. In the past, land managers didn’t understand how important fire was and so they prioritized fire suppression (mostly because fires threaten homes and businesses nearby). Smokey the bear became an icon for anti-fires in all ecosystems, and until the 1980s, natural fires were put out and there were no prescribed (or controlled) fires. Smokey imprinted fire as bad for many of us as kids, and a 6-foot tall Smokey is still posted right in front of the pinelands on Big Pine Key. However, as we’ve discussed, without fire, diversity is lost.

Natural fire, started by a lightning strike, would normally burn the whole island, but now the islands are fragmented with homes and roads, which would require multiple lightning strikes. This is why prescribed fires are needed. Smokey has scared people that are not familiar with their own backyard forests, especially since many people now live where they didn’t grow up.

There have been a lot of fires in the news lately. What’s missing from the messages being conveyed?

There doesn’t seem to be recognition of the different types of forests and whether they are fire-dependent or not. Not all fire-dependent ecosystems are the same, there’s actually a large variation. California forests naturally have a fire every 30–60 years (sometimes several 100). However, we’ve suppressed fire for so long that the fuels build up for a long time, so that when they do happen, fires are more severe and intense (2018 saw the deadliest fire season ever in California). The fires in the Canary Islands are being portrayed as terrible, but that habitat is fire-dependent and fires should naturally occur every 15–20 years there. The fires in the Amazon, however, are occurring in rainforest, a habitat that rarely naturally burns. The cause is likely similar to those in Siberia—human induced fires to cover up illegal logging or facilitate cattle and agriculture.

What’s the inspiration for your work on this?

I’m originally from New Orleans, and I wanted to study hurricane disturbance. Disturbance drives variation and diversity across landscapes. I was interested in small scale (fire) vs. large scale (hurricane). I did my Masters on the effects of pesticide spray on plants and pollinators. While doing my fieldwork for this I realized that there were noticeable patterns of differences in flowering based on fire frequency, so I have focused mostly on fires for my PhD research. 

Moral of the story:

We need to re-shape Smokey, starting fires is not good, but not all fires are bad. In order to maintain biodiversity and to prevent bigger fires later, we have to let some fires happen, we can’t control nature. As conscientious citizens we can also try to reduce our meat/beef consumption to decrease the demand for South American beef, use recycled paper products, avoid products made with exotic wood (upcycle!), and contact your elected officials to voice support for the rainforest.

Follow Brittany on Instagram @brittanmh