Why Save Our Past?

Highland cattle, a breed which originated in the Scottish Highlands, is the oldest registered breed in the United States. (Photo credit: Photodisc/Getty Images)

A hundred years ago or so, there was plenty of variety in agriculture. Worldwide, farmers raised thousands of different animal breeds and grew just as many varieties of plants. As farms grew bigger and became more industrialized, however, fewer and fewer species were used as crops and livestock. [Read more…]

Top Predators and Ecosystem Health

The presence of predators is a key indicator of ecosystem health. (Photo credit: Doug Smith/NPS)

Ecologists have long known that the health of an ecosystem depends on productivity at its base. Known as “bottom-up” control, nutrients available at the bottom of a food web dictate the abundance of organisms at each trophic level above it. But now mounting evidence is turning the bottom-focused theory on its head, pointing to the key role played at the very top of the food web.

Although they make up little of an ecosystem’s total biomass, top predators help regulate the entire web. For example, sea otters are a top predator in the kelp forests of the Pacific Ocean. When the sea otter population dropped, sea urchins went unchecked and decimated the kelp forests. As a result, many other species that depended on the kelp forests also declined, including raptors, shorebirds, fish, and invertebrates. Now that sea otters are protected and their numbers are back up, the kelp forests and the species  that depend on them are recovering as well.

If such chain reactions, or trophic cascades, are common to other ecosystems, there could be major implications for conservation. Top predators of terrestrial ecosystems such as wolves, bears, jaguars, and lions have declined throughout the world due to human activities. In North America and Eurasia, wolves in particular have been eradicated from many areas where they were once widespread. If the wolf populations were required to keep their prey populations in check, we would expect to see much higher numbers of deer, caribou, elk, and moose in those areas. We would also see changes in the plants the herbivores consume, as well as impacts to the biodiversity those plant communities harbor.

A recent study at Oregon State University set out to look at that very data. Researchers analyzed published data on populations of wolves, bears, and cervids (members of the deer family) in boreal and temperate forests of North America and Eurasia from 42 separate studies. They used remote sensing imagery to identify productive forests and historical range maps to determine areas where wolves and bears have gone locally extinct.

The investigators used statistical analyses to compare cervid density in forests where top predators remain to areas where they have been removed. What they found was strong evidence for “top-down” control of herbivores by predation. The average cervid density was almost six times greater in areas with wolves than areas without them.

Many authors of the reviewed studies also noted impacts of unrestricted cervid populations on the rest of the ecosystem. They observed declines in specific tree and shrub species, as well as changes to invertebrate communities. Other effects included increased stream bank erosion, which has led to changes in stream shape and fish habitat.

The researchers’ analysis also revealed that, although humans hunt deer, humans do not adequately stand in to fill the role of the top predator. The reason may have to do with how humans hunt compared with how large mammalian carnivores hunt. Apparently, the presence of predators does more than just limit a population’s numbers; it also affects how they behave.

When wolves were reintroduced to Yellowstone National Park in the mid-1990s after almost a 100-year absence, elk populations not only shrunk but also changed their behavior. They moved to safer areas, avoiding the riparian ecosystems which have since made a striking comeback. Vegetation came back to the stream banks along with beavers, beaver dams, and the fish and bird habitats they create.

As a strategy for habitat restoration, then, reintroduction programs or protection programs for top predators may yield far-reaching results. But they must be implemented with careful planning. Wolves have not historically been ranchers’ best friends, and their reintroduction in and around Yellowstone has been rife with controversy. One organization, Defenders of Wildlife, has come up with a creative solution to overcome ranchers’ losses due to wolves by paying them for killed livestock.

However, one thing is becoming clear from the mounting data on the complexities of ecosystem regulation: no one can do it quite like the top predators. It’s a job best left to the wolves.

More to Explore

The Reintroduction of Wolves to Yellowstone 
Top-Down Regulation
Defenders of Wildlife

Hawaiian Agriculture and Its Impact on the Environment

Hawaii’s mild climate is ideal for year-round agriculture. (Photo credit: USDA)

Hawai’i has been associated with agriculture for as long as the islands have been inhabited. In some ways, the Hawaiian Islands are a perfect place to farm. A mild climate allows a year-round growing season. The average high temperature in July is 25° C (77° F), and the average low in January is 21° C (71° F).  Plenty of rainfall creates rich soil as nutrients from plant material get incorporated into the earth below.

Even so, early Polynesian settlers had to pick their farming sites carefully. The islands were once active volcanoes, and the lava flows range from hundreds of thousands of years old to brand new. The ancient flows make for good farmland now, but all of the land is patchy due to the newer lava flows lying on top of older flows in some places. Also, some areas get copious amounts of rainfall, and some areas receive almost no consistent rain. Too much rain washes nutrients right out of the soil and too little rain won’t allow crops to grow. Archeological studies have concluded that rainfall and soil types were deciding factors for the early settlers when choosing where to farm.

The first Polynesian voyagers, arriving from other Pacific islands, brought with them produce such as bananas ( mai’a in Hawaiian) and taro (kalo). Taro is farmed in lo’i, which are irrigated fields similar to rice paddies.  Because taro needs a continuous supply of fresh water, taro lo’i diverted water from streams. The water was then returned to the stream for use by the next farmer. They also created fishponds along the coast to raise seafood.  Each of the lo’i along the stream would add nutrients to the water, and the same stream would eventually add nutrients to the fishponds. For hundreds of years before the arrival of westerners, Hawaiians lived closely with the land and were able to sustain themselves. They divided up land with island ecology in mind. The land divisions, called ahupua’a, created pie-shaped slices of land from the mountains to the ocean.

When Captain Cook, the first westerner, arrived on the islands in 1778, he found not only taro and banana but sweet potatoes, pigs, chickens, ginger, sugar, coconut, and uniquely Polynesian crops like breadfruit (ulu), kawa and ti plants.  Eventually, rice was introduced and taro farming declined.  Sweet potato crops were devastated by the introduction of disease. The era of big sugar plantations began in 1834. Macadamia nut and pineapple plantations followed, using thousands of acres of land. In 1922 James Dole bought the entire island of Lana’i, using much of it for growing pineapple.  In 1959, Hawai’I became the 50th state.

Today, there are about 7,500 farms in Hawai’i, which use more than a million acres of land. Tropical plant and flower nurseries are one of the top money makers for Hawai’i, but this business has also caused the introduction of alien species. The coqui frog, a tiny little frog with a big voice, is well loved in its native Puerto Rico. It has been accidentally introduced in Hawai’i, where it has not received a warm welcome. Large populations of the frogs have been established on several of the islands, and, while they do not harm crops, they have cost many tourism dollars and lowered the property value of many homes. When groups of coqui sing in the evenings, the noise is above the decibel standards for hearing safety. In addition, nurseries now often have to certify that their plants are “coqui-free” which has created additional expenses for these companies.

Insects, too, have hitched a ride across the ocean from other tropical locales in the nursery trade. Interestingly, Hawai’i has one of the best quarantine programs in the world to prevent non-native species from establishing themselves. Even back in 1888 King David Kalakaua recognized the importance of quarantining products brought to the islands. He quarantined imported coffee to prevent the introduction of disease to the coffee crop. Today, tropical plants from other places are not allowed to be sold in Hawai’i. What is allowed, however, is to ship plants to the islands with the intention of bringing them them to the mainland United States or other global destinations. Sometimes, however, the plants have passed customs inspections in Hawai’i and then have been illegally distributed on the islands.  Now bug infestations, such as non-native fruit flies, prevent some companies from buying plants from Hawai’i.

Hawai’i has moved a long way away from its subsistence farming roots. It is currently 42nd in the United States for agricultural product sales, and imports at least 90% of its products. One estimate says that Hawai’i only has enough food for its current population to last 7 days. Still, agriculture is important to Hawai’i. It is the 3rd largest revenue producer, after tourism and the U.S. military. Agriculture adds almost 3 billion yearly to the state’s economy, and provides 42,000 jobs. High-tech aquaculture firms have replaced traditional fishponds. However, the pineapple and sugar industries that were once so vast are rapidly shutting down due to cheaper production in other places worldwide.  Lanai’s pineapple fields, for instance, have returned to grassland. Feral pig and goat populations on all the inhabited islands have endangered native plant populations. Many of the native species are endemic to Hawai’i, meaning they are found nowhere else in the world.

Modern challenges to farming on the islands center on the high cost of land. Many farmers must lease their land so they are reluctant to buy expensive equipment when there is a chance they may lose the land they farm on. Cost of irrigation, workers, and transport of the harvest all add to the cost of farming. One of the possible solutions to both preserve the environment and increase agriculture revenue is agri-tourism. Tourists are increasingly looking for cultural and unique hands-on experiences during their vacations.  Flower farms, cattle ranches, coffee and macadamia nut plantations, and fruit orchards have all started exploring this option. Chefs that cook with local foods are also using tourism to support agriculture. Marketing products as Hawaiian is also helping sales. Macadamia nuts and coffee are two products that are especially associated with Hawai’i. Coffee grown in Hawai’i is the only coffee grown in the United States, and macadamia production in Hawai’i is second in the world.  Products labeled “grown in Hawai’i” can command a higher price around the world than the same products grown elsewhere. Farms dedicated to preserving traditional farming techniques are also on the rise. Traditional farmers must also be environmental activists, lobbying for water once used for plantations to be returned to streams for taro lo’i.  The lo’i are popping up again on the islands, as more island residents recognize the wisdom of traditional diets and farming practices that preserve Hawai’i’s unique environment.

More to Explore

Hawai’is Agriculture Facing the Future 
To Hawai’i Travel Guide: Agriculture of Hawai’i
Hawaii Department of Agriculture
History of Agriculture in Hawai’i
Hawaiian Soils Reveal Clues to Cultural History

Society and the Environment: Changing Seas

catching fish

Overfishing from higher trophic levels means commercial fishers must harvest from lower trophic levels to meet demand.

Most of the food we eat comes from agriculture and farming, but we also rely on the fishing industry. About 15% of the animal protein consumed in the world comes from fish and other marine and aquatic organisms. But many fish species have been overharvested. The swordfish and cod fisheries of the North Atlantic and the salmon fishery off the northwestern coast of the United States are examples of depleted fisheries. In many parts of the world, sharks are disappearing rapidly because of the demand for shark fin soup. Some fisheries now contain so few fish that harvesting them is not economical. And the size of some of the harvested fish that remain are now smaller because they don’t survive long enough to grow.

[Read more…]