Fires, flowers, and forests in Guanacaste, Costa Rica

I lace up my boots and clip snake-gators around my shins. I pull my machete from the leather sheath and whet it across the sharpener as the sky shifts from pale orange to blue. The iguana that lives in the roof, discontented with my noise; shuffles above me, his long toes scratching the tin. I glance over at the field bags and go through a mental check list of the equipment to make sure I haven’t forgotten anything: datasheets, compass, soil samplers, flagging, ziplocks, sharpies, caliper, DBH tape. Check, check, check. My research assistant, Juan, and I load the field equipment into the car and head down the bumpy dirt road.

I am in Guanacaste, Costa Rica, and it is nearing the end of the dry season. It hasn’t rained since November. Occasionally a wispy cloud will dampen the sun’s strength and I’ll look up, confused. The dry season feels like a washed-out photo; everything is overly bright and I squint in search of contrast. My car’s dash board is covered in a thick film of dust from driving on farm roads. Waves of dusk billow up from the roads and pass through the window in sets so consistent a surfer could set her watch by it.
Guanacaste province gleaned it’s named from the wide-canopied dry forest tree with seedpods shaped like ears. Guanacaste is one of the larger provinces in Costa Rica, bordered on the north by Nicaragua and on the west by the Pacific Ocean. I am here studying tropical dry forests; one of the earths most endangered ecosystems.

For part of the year in Costa Rica, moisture-laden warm air flows off the Caribbean Ocean. The warm air pushes up against Costa Rica’s volcanic spine, cooling as it rises, until it reaches the dew point and rain falls on the windward slope, creating a rain shadow on the other side of the mountain. The leeward slope, then, is haunted by intense dry winds. During the other half of the year, the winds come off the Pacific Ocean, bringing the rains. Tropical dry forest fauna and flora have evolved to cope with the strong seasonality to the rainfall.
When I arrived last September, the forest was as green as a summer garden. Leaves broad, full, verdant. The drought-deciduous trees species began to lose their leaves when the rains stopped. Now in April, a mountaintop view looks not unlike a temperate winter landscape—if you replace the thin-needed pines with broad-leaf evergreens, subtract the snow, and spin the thermostat up to 95 degrees F. Okay, so they are quite different: no coat required. Also, many TDF trees flower during the dry season so, amidst the mostly nude forest, bouquets of yellow, pink, purple dot the landscape.

The car windows are wide open and the wind rolls through carrying a campfire smell. The air often smells burnt during the dry season, especially in the last couple months. Before people settled in Guanacaste, the main source of fire would have been lightning—in the wet season. People have introduced a fire regime that peaks in the driest months. I drive out of the trees and notice the smoke on the road ahead. The dry, reedy pasture grass on farms on either side of the road is aflame. I have worked on both of these farms. I can see a few trees burning and a wall of hazy smoke across the asphalt. My car hits the smoke and it swirls off the car in tornados.

TDF have been disproportionately settled because it has relatively nutrient-rich soils and a climate favorable for growing crops and raising livestock. And if you’ve ever lived in a tropical rain forest or cloud forest—you’ll know that even freshly laundered T-shirts, folded and put away in a clean dresser begin to smell like the musty back corner of a forgotten part of your garage within a few days. It’s no wonder people preferred sunshine.
I glance in the rearview mirror and can still see the smoke lifting from the fire we passed. Although management patterns are changing, some people still use fire to “clean” pasture. They burn pastures to clear out early forest successional growth and entice new pasture grass to sprout for hungry livestock. Also, crops like sugar cane are burned after the harvest to remove crop residues. Landowners can apply for a burn permit with the Costa Rican Ministry of Environment but illegal burns are common. Regardless of the source or legality of the burn, once a fire escapes, landowners face another problem; there are not enough resources to fight forest fires on private farms. There are fire fighters. Area de Conservación de Guanacaste (ACG), with upwards of 290,000 acres of land, has a trained team firefighters that are kept busy protecting both the immense park and bordering forests on private farms. City fire fighters, on the other hand, must focus their efforts on fires that encroach upon buildings, towns, and roads. Basically, there are not enough resources to fight all the fires on private farms. If the landowner has employees and equipment, they will often fight the fires. But, frequently, the private forests just burn. I drive past the road that runs up the flanks of Rincón de la Vieja volcano. When I was hiking there last week, I stopped at a lookout point and counted seven fires. They looked like industrial smokestacks scattered in the forested landscape.
Guanacaste is in the middle of a forest transition. In the 1970s and 1980s deforestation rates were high, but beginning in the mid-1980s Guanacaste has had high rates of forest regeneration. Importantly, the overwhelming majority of that regeneration has occurred on private lands. What I’m trying to find out is who owns these regenerating forests and how ownership might influence the ecology and management.
I am interested in coupled human-natural systems—intrigued by the links between society and environment. Here in Guanacaste I am looking at how tree biodiversity and carbon storage are influenced by socioeconomic variables such as land ownership. I am interested in how the choices landowners make could influence forest regeneration processes. For example, ranchers retain certain tree species on their lands for the shade or fruit provided for their cattle. Landowners often select particular species such as indio desnudo (Bursura simaruba) to use as live fence posts—fences made of living trees connected by lines of barbed-wire. Indio desnudo is a great live fence post tree because it resprouts so easily: You can cut off a branch, plunk it in the ground and, viola, you’ll get a tree. Landowners may also be more likely to remove ‘weedy’, fast growing species from their pastures and retain valuable timber species such as mahogany (Swietenia macrophylla). These choices may influence the forest biodiversity and carbon stocks in private forests. After completing forest inventory plots on private farms, I will compare my data to a dataset from public forests collected by my adviser. We will use these datasets to test the hypotheses that private forests contain less biodiversity and carbon stocks than public secondary forest of similar ages and soil conditions.

Juan and I arrive at our new farm site. I stop briefly to talk with the farm manger; he is sitting atop a big tractor outfitted with a water container to fight the fires that are on the upper border of the property. Juan and I will work on the lower border of the property to avoid the fires. We drive to the lower part of the property and Juan hops out to struggle with the gate—five wrist-thick branches strung together with barbed-wire. The car lumbers down the road through the pasture and we arrive at a patch of forest. In the forest plot today, we will identify tree species to assess tree biodiversity. For carbon estimates, we’ll measure tree diameter at 1.3 m take species-specific wood density samples to plug into allometric equations. Within the plot, we will also collect soil samples to assess soil physical and chemical properties. We heft on our backpacks and swing the field bags over our shoulders. I rope the machete around my waist in case I need to give the spiked bromeliads in the forest plot a haircut.