About Author: Christa Horn

Posts by Christa Horn


The Right Tools

Two boys admire aguaje fruit, an important resource in the Peruvian Amazon.

Sometimes all you need is the right tools.

In August 2010, I spent three weeks trudging through swamps in the Peruvian Amazon to assess the aguaje palm population on the lands of an indigenous group known as the Maijuna. Aguaje is an avocado-sized fruit with smooth scales covering a thin layer of bright orange flesh. It is high in Vitamin A and very popular in the large Amazon city of Iquitos. As a result, rural communities from all over the region, including the Maijuna, harvest aguaje to supply the city’s demand. But the tree’s height (up to 90 feet or 27 meters!) means that the fruit is often harvested by cutting the palms down.

Aguaje fruit awaits buyers in the market place. It is spread out so shoppers can assess the quality.

The extreme heights are also difficult to measure, and attempting to do so in the boot-suctioning mud of the swamps wasn’t always easy for us in the field. But the animals don’t mind: a plethora of wildlife, including monkeys, parrots, tapirs, and peccaries, are known to frequent the aguaje palm swamps to feast on the fruits.

While I was in the swamps, Michael Gilmore of George Mason University conducted interviews with Maijuna villagers. The objective of our combined work was to better understand the management needs of aguaje. A few years ago, the Maijuna decided to reclaim sovereignty over their natural resources by keeping outsiders, especially loggers, from coming onto their lands and better managing their own use of the land’s resources. This included finding a better way to harvest aguaje without killing the palms, and some of the community members learned to use climbing harnesses to reach fruit at the top.

A group of community members shows off their new climbing harnesses. Every household with a member attending the workshops received a harness.

But not everyone could climb. What Michael found out in the interviews was that, for many families, no one knew how to climb, so some continued to harvest the old-fashioned way, with an ax, even though they knew of the consequences. Even people who knew how to climb would sometimes use axes. What struck me, however, was how many families said they just stopped harvesting fruit because they didn’t know how to climb and wanted to conserve the palm trees. That is awesome! It shows a commitment to sustainable management and that the people place a high value on the future of the resource. But it also means those families are missing out on a potential source of income. When the average family income is just over $500 a year, the few dollars made from selling some sacks of aguaje can make a big difference. This partially explains why some people continue to cut.

Key to workshop success was ample time for attendees to practice climbing. Practice allows people to become comfortable at the extreme heights needed to reach the fruit.

After our assessment in 2010, it was clear that the Maijuna needed more training. And more equipment. The 37 households in the 2 villages were sharing a handful of harnesses, and they weren’t always available when needed. So in 2011, we held climbing workshops and invited everyone from the villages. We shared our study results, but most people were already aware of the negative impacts of cutting palms. We focused on hopeful things: there are a lot of seedlings and saplings growing in the damaged swamps that will provide fruit in the future. And we gave the people a lot of time with the expert climbers. Everyone got to practice and get comfortable with the climbing harnesses. We also wanted every household to have the right tools, so every household received a harness.

We didn’t expect the workshops to solve everything. The stands of aguaje palm need to recover from the years of destructive harvesting. But things did improve—a lot. In 2012, we went back to evaluate. Even though many more families harvested and the community harvested 50 percent more sacks of fruit, the number of cut palms went down. And now, instead of over half of the palms harvested being cut down, only about 14 percent were. To me the encouraging sign is how many more families were harvesting fruit, now that they knew how to climb. Their willingness to restrain from harvesting before, even though they would have liked to, shows commitment to resource management. All they needed all along were the knowledge and the tools for better management practices.

That’s San Diego Zoo Global’s role in this project: trying to figure out the best tools for the community’s goals and help them obtain those tools. Next with aguaje, we’ll be working with the community to figure out the best ways to improve the stock of aguaje palms on their lands. We want to make sure there’s enough aguaje for both wildlife and people.

Christa Horn is a research coordinator in the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research. Read her previous post, A Grand Experiment for Palm Trees.


A Grand Experiment for Palm Trees

Measuring Sinolao hesper palms in Sonora, Mexico

Christa is part of a research team focusing on a threatened palm and how various management practices (i.e. cattle grazing) affect its population in the Sierra de Alamos-Rio Cuchujaqui Protected Area in the state of Sonora, Mexico. Read her previous post, Conserving Threatened Palms.

Looking across the arroyo, where our experiment is set up, at the hundreds of Sinaloa hesper palms Brahea aculeate dominating an area the size of a football field, I have to remind myself that we are working with a palm listed as “vulnerable” on the IUCN (International Union for Conservation of Nature) Red List and “threatened” by the Mexican government. Such large populations are rare across the palm’s range, which includes parts of just three Mexican states. Even in the small sea of palms before me, I see signs that the population is stressed: the number of seedlings is conspicuously low, few adult palms produced fruit or even flowering racemes in the past year, and a number of dead trunks dot the population.

Hesper palms in a plot in the arroyo

None of this is terribly surprising, given the stressors we know the population has been subjected to, namely years of cattle grazing and intensive leaf harvesting. The cattle munch on the shorter palms during the driest time of the year, as the palms are one of the few green things on the landscape. Local people harvest palm leaves to make roofs that are quiet in the summer rains and keep a home relatively fresh and cool during the dry season’s heat. Such roofs are also popular for restaurants and other tourism facilities along Sonora’s west coast. The loss of leaves from cows or people doesn’t usually immediately kill the palm, but with the need to put on many new leaves, the palms may not have energy left to produce fruit. Some may not even be able to recover fully from the leaf loss and slowly die. Though both result in leaf loss, the impacts of harvesting and grazing may be different: they affect slightly different size classes of palms, vary in the completeness of defoliation, and have different secondary impacts (i.e., trampling hooves). And we don’t know exactly how either is affecting the population.

A palm shows the sad results of a high harvest.

In the experiment set up in the arroyo, Postdoctoral Fellow Leonel Lopez-Toledo is attempting to tease out the effects of the two stressors. We have rented two plots from a local rancher and built a fence around one to keep the cattle out. Each plot is divided into three parts: no leaf harvesting, low-harvest intensity, and high-harvest intensity. The low- harvest intensity spares the youngest leaves and follows other rules of thumb used by harvesters in the local communities. The high-harvest takes everything useful and is what is typically done by people who come from cities and coastal communities. We will then track every palm—all 1,500 or so—for the next few years, measuring growth, changes in leaf length and shape, number of leaves put on, number of fruits produced, and more. Each year we hope to see how the palms are responding to the different treatments and what these responses may mean for the palm population as a whole.

Our field assistants come from the local communities and were clearly uncomfortable mimicking the outsiders’ high-harvest approach. I’m sure the sight of the completely leafless palms was just as disconcerting to them as it was to me. On the other hand, their traditional low-harvest rules may be sustainable.

A rare hesper palm seedling

If Leonel’s experiment can demonstrate that it is, the next step would be to work to make the low-intensity harvest an enforceable rule—for outsiders as well as locals. The grazing part of the experiment may lead to recommendations in range management or restoration for the ranch owners. Getting actual changes from the recommendations would be challenging, to be sure, but limiting the stress these threatened palms are under will be key to their survival, especially in the face of other stressors such as climate change.

However, step number one is to flesh out the problem. So, I turn back to the small sea of palms, ready to start measuring.

Christa Horn is a senior research technician in the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research.


Conserving Threatened Palms

The threatened palm Brahea aculeata

The descriptor “tropical forests” usually conjures images of lush green forests with high canopies brimming with life—or at least for me it did. But as I look across the lands of the Sierra de Alamos-Rio Cuchujaqui Protected Area in Sonora, Mexico, I see large, columnar cacti peeking out from the fading green and pale brown of surrounding trees. Yet this, too, is considered a tropical forest—a tropical deciduous forest. Here the lush green foliage bursts forth with the summer monsoons and extends through mid-fall and hurricane season. As winter approaches, the trees drop their leaves, though not because of the cold temperatures, as with temperate forests, but due to the dry climate. By March, there is nary a leaf in sight, and the hillsides have taken on a red-brown-gray referred to locally as mojino. Many of the adaptations we associate with desert plants developed here to survive the harsh, dry season. The green that remains is found along the arroyos and in the stems of the tall cacti. That’s not to say there is no color, for during the dry season there is always something flowering. Blooming amapas Tabebuia impetiginosa add a splash of color to the fading greens and brown as we drive to the protected area.

A hawk perches on an amapas tree. Click on the photo to enlarge.

But the image of a forest brimming with life still fits, even if the first view doesn’t confirm it. Thousands of plant species live here, many are found only here. The Sierra’s tropical deciduous forest supports a rich array of fauna as well. With over 450 resident and migratory bird species, and many recognized as threatened or endangered, Birdlife International has designated the Sierra de Alamos as an Important Bird Area. The area also provides essential habitat and corridors for charismatic megafauna such as jaguars, ocelots, and margays. Many tropical amphibian and reptile species reach their northern range limits here, while desert species, such as the Gila monster, also extend into the region.

The protected area where we are working represents the northernmost stretch of tropical deciduous forest in the Americas, and possibly the most intact. Once extending from here in southern Sonora to Panama, and usually with only a width of around 30 miles, only 15 percent of the tropical deciduous forest in North America remains. And only about 1 percent of that is in protected areas. Though rather unusual for a protected area, the majority of lands in the Sierra de Alamos-Rio Cuchujaqui Protected Area remain in private hands; the reserve limits activities such as mining and land clearing, but cattle ranching still dominates the land, and overgrazing prevents a large risk. As part of the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research, I’m here as part of a research team focusing on a threatened palm, Brahea aculeata, and how various management practices (i.e. cattle grazing) affect the palm population.

Nature and Culture International (NCI), a nongovernmental organization partnering with San Diego Zoo Global in several locations in Latin America, represents an important resource for our project. They own land, have staff who serve as excellent field assistants and guides, and have strong relationships with ranchers in the area. Seeing the importance in conserving this little-known corner of the tropics, NCI has taken on the task of adding more stringent protection by purchasing the ranches along the main watershed. With just a few years’ break from cattle, it is easy to distinguish NCI lands from neighboring ranches; willows and other riparian vegetation really do flourish without the constant munch of cows. Hoping to widen its impact beyond the landholdings, NCI is working with us on some land-management issues in the area. We hope to base management practices in science and share them with the neighboring ranches. Building on this partnership, we hope to conserve this special part of Mexico, the tropical deciduous forest and the wonderful wildlife it contains.

Christa Horn is a senior research technician in the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research. Read her previous post, Observing Nature as a Child.

For more information on NCI and San Diego Zoo Global’s partnership…

For more information on the tropical deciduous forest of Sonora and NCI…


Observing Nature as a Child

A young Christa

October is Kids Free Days at the San Diego Zoo and San Diego Zoo Safari Park. We’d also like to encourage children to get outside and explore nature. During October, staff at the San Diego Zoo Institute for Conservation Research are sharing their interactions and connections with nature at a young age and how these connections put them on their paths to becoming conservation biologists. Read the previous post, No Child Left Inside.

In my father’s favorite picture of me as a child, I am crouching on a forest floor, smiling up at the camera with a face covered in dirt. I’m told it was a common scene: the curious little girl leaning in for a closer look at pine needles, insects, rocks, or just the different colored soil, and getting her hands (and everything else) dirty.

Until about the time I started junior high, my family regularly packed up the tent trailer for a weekend of hiking or fishing. Spring trips might be to Death Valley, where we could play in the dunes and enjoy the desert stars. In the summer, we would escape the heat of our high desert home by heading up the Eastern Sierras. I wasn’t much of a fisherman, but I loved sitting on the banks or fording streams barefoot. On hikes I would work to stay ahead of my dad and my sister to be the leader, at least until something on the side of the trail distracted me or I needed my dad to dig into the backpack for a snack.

When not on family excursions, I spent my most of my childhood either playing outdoors or reading a book. I held tea parties in the gap between two juniper shrubs in the corner of our backyard. When my sisters and I played “house,” our make-believe house was usually a shallow hole ringed with creosote bushes in the desert lot next to our family’s home; one creosote bush would be the kitchen area and another a bedroom. Though I was the worst lizard hunter, I enjoyed watching them do push ups on rocks or testing how close I could get to them before they scampered away. My sisters and I regularly collected fuzzy creosote seeds to throw in each other’s hair while pulling apart stork’s bill seeds to watch them curl up into a corkscrew. Whether at home or on trips, I always enjoyed observing nature and seeing something new.

Neither of my parents would consider themselves naturalists, of even the amateur variety, and I rarely learned the names of the plants or animals I saw. But they encouraged me to observe and explore. Now, when I go back to the Sierras, it is with different eyes. Upon finding an unknown flower I can look it up and learn its name, I wonder about the speed of regeneration after a fire, or what limits the range of the different conifers. But it all starts with making observations, something I practiced a lot as a child.

Christa conducts field work in the Amazon.

Though outdoor play decreased as school sports and the daily trials and tribulations of adolescence kicked in, my love of the outdoors never extinguished. This love, combined with the intellectual stimulation of a university setting, became first a major and eventually a career. Incredible field experiences as a student paired the outdoor exploration I had always enjoyed with the knowledge to ask more refined questions and learn through scientific research.

Today, as a senior research technician at the San Diego Zoo Institute for Conservation Research, I work on projects right here in San Diego County as well as exotic locales, such as the Peruvian Amazon. Not only do I enjoy my job, but I take great pride in knowing my work contributes to the conservation of plants and animals. I spend a good portion of my time outdoors “in the field” setting up research projects, taking data, or just making observations, which to my father means I am still the curious little girl going out and getting herself covered in dirt.

Christa Horn is a senior research technician in the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research.