Reading Test 11
The Dinosaurs Footprints and Extinction
A
EVERYBODY knows that the dinosaurs were killed by an asteroid. Something big hit the earth 65 million years ago and, when the dust had fallen, so had the great reptiles. There is thus a nice if ironic, symmetry in the idea that a similar impact brought about the dinosaurs’ rise. That is the thesis proposed by Paul Olsen, of Columbia University, and his colleagues in this week’s Science.
B
Dinosaurs first appeared in the fossil record 230m years ago, during the Triassic period. But they were mostly small, and they shared the earth with lots of other sorts of reptile. It was in the subsequent Jurassic, which began 202 million years ago, that they overran the planet and turned into the monsters depicted in the book and movie “Jurassic Park”. (Actually, though, the dinosaurs that appeared on screen were from the still more recent Cretaceous period.) Dr Olsen and his colleagues are not the first to suggest that the dinosaurs inherited the earth as the result of an asteroid strike. But they are the first to show that the takeover did, indeed, happen in a geological eyeblink.
C
Dinosaur skeletons are rare. Dinosaur footprints are, however, surprisingly abundant. And the sizes of the prints are as good an indication of the sizes of the beasts as are the skeletons themselves. Dr Olsen and his colleagues, therefore, concentrated on prints, not bones.
D
The prints in question were made in eastern North America, a part of the world the full of rift valleys to those in East Africa today. Like the modern African rift valleys, the Triassic/Jurassic American ones contained lakes, and these lakes grew and shrank at regular intervals because of climatic changes caused by periodic shifts in the earth’s orbit. (A similar phenomenon is responsible for modern ice ages.) That regularity, combined with reversals in the earth’s magnetic field, which are detectable in the tiny fields of certain magnetic minerals, means that rocks from this place and period can be dated to within a few thousand years. As a bonus, squishy lake-edge sediments are just the things for recording the tracks of passing animals. By dividing the labour between themselves, the ten authors of the paper were able to study such tracks at 80 sites.
E
The researchers looked at 18 so-called ichnotaxa. These are recognizable types of the footprint that cannot be matched precisely with the species of animal that left them. But they can be matched with a general sort of animal, and thus act as an indicator of the fate of that group, even when there are no bones to tell the story. Five of the ichnotaxa disappear before the end of the Triassic, and four march confidently across the boundary into the Jurassic. Six, however, vanish at the boundary, or only just splutter across it; and three appear from nowhere, almost as soon as the Jurassic begins.
F
That boundary itself is suggestive. The first geological indication of the impact that killed the dinosaurs was an unusually high level of iridium in rocks at the end of the Cretaceous when the beasts disappear from the fossil record. Iridium is normally rare at the earth’s surface, but it is more abundant in meteorites. When people began to believe the impact theory, they started looking for other Cretaceousperiod anomalies. One that turned up was a surprising abundance of fern spores in rocks just above the boundary layer – a phenomenon known as a “fern spike”.
G
That matched the theory nicely. Many modern ferns are opportunists. They cannot compete against plants with leaves, but if a piece of land is cleared by, say, a volcanic eruption, they are often the first things to set up shop there. An asteroid strike would have scoured much of the earth of its vegetable cover, and provided a paradise for ferns. A fern spike in the rocks is thus a good indication that something terrible has happened.
H
Both an iridium anomaly and a fern spike appear in rocks at the end of the Triassic, too. That accounts for the disappearing ichnotaxa: the creatures that made them did not survive the holocaust. The surprise is how rapidly the new ichnotaxa appear.
I
Dr Olsen and his colleagues suggest that the explanation for this rapid increase in size may be a phenomenon called ecological release. This is seen today when reptiles (which, in modern times, tend to be small creatures) reach islands where they face no competitors. The most spectacular example is on the Indonesian island of Komodo, where local lizards have grown so large that they are often referred to as dragons. The dinosaurs, in other words, could flourish only when the competition had been knocked out.
J
That leaves the question of where the impact happened. No large hole in the earth’s crust seems to be 202m years old. It may, of course, have been overlooked. Old craters are eroded and buried, and not always easy to find. Alternatively, it may have vanished. Although the continental crust is more or less permanent, the ocean floor is constantly recycled by the tectonic processes that bring about continental drift. There is no ocean floor left that is more than 200m years old, so a crater that formed in the ocean would have been swallowed up by now.
K
There is a third possibility, however. This is that the crater is known, but has been misdated. The Manicouagan “structure”, a crater in Quebec, is thought to be 214m years old. It is huge – some 100km across – and seems to be the largest of between three and five craters that formed within a few hours of each other as the lumps of a disintegrated comet hit the earth one by one.
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ECOTOURISM
If you still believe the once-commonly held misconception that tourism is only an indulgence for the wealthy, you are out of step with the times! The tourism market is accessible to, and indeed marketed toward, many different sections of the community. Adventurers, fitness freaks, nature-lovers, and business people all contribute to a rapidly expanding sector of the global economy.
Section A
This billion-dollar industry, whilst affected slightly by the unforeseen events of 11 September 2001, has experienced significant growth since the late 1980s. The subsequent economic benefits for governments are well-documented as tourism boosts foreign investment and foreign exchange. Large-scale resorts and civil infrastructure were often the only response to successful marketing and increased tourist demand. It is not surprising then that the direct impact on the environment and regional or indigenous populations became a contentious issue. Governments and big business became the target of environmentalists and activists who argued that mass tourism was not (and is not) sustainable. As hordes of tourists descended on often overcrowded beaches and overused parklands, this became apparent. Eco-tourism was born.
Section B
The broad concept of eco-tourism as a nature-based, culturally sensitive form of tourism was taken up enthusiastically because there appeared to be few losers. Governments were given a convenient escape route as eco-tourism appeased the environmentalists and local communities but still provided income. Environmentalists saw eco-tourism as an alternative to mass tourism and its resource-exploiting ways. Local communities envisaged receiving at least a percentage of the tourist dollars, creating job opportunities and giving them control over the impact on their own communities. It seemed that the benefits of mass tourism were going to be expanded in the new world of eco-tourism to include cultural, social and environmental elements.
Section C
As evidence of the benefits of eco-tourism unfolded, the practice has spread. So much so that the United Nations nominated 2002 as the International Year of Eco-tourism. Perhaps inevitably, the meaning of ecotourism became less clear as it enveloped the globe. It could be argued that the form of eco-tourism adopted in some cases was found wanting in certain aspects and the need for agreement on a tighter definition resulted. The eco-tourist is one who does not wish to contribute to the negative impact of large-scale tourism. He/she generally travel in small groups to low-key developments and attempts to “tread lightly” on the earth. These smaller-scale developments are environmentally responsible with a view to sustainability in all of the resources used. Their landscaping often relies on the use of native flora and they incorporate recycling methods and energy-efficient practices. Within the eco-tourists, holiday experience will be an element of education about the local environment. The emphasis is on conservation and the part that humans play in keeping ecosystems functioning. If the area is of cultural or social importance, this is recognised. The eco-tourist doesn’t condone the exploitation of the indigenous or repatriation of funds to external sources is frowned upon. Wherever possible, the benefits of an eco-tourist’s holiday should be shared with the regional community — the hosts.
Section D
All of these elements promote minimal impact on human resources as well as physical, cultural and environmental ones. They support conservation through education and experience. Despite the best of intentions, as the popularity of eco-tourism spreads, there is concern that the eco-tourist will have a more adverse effect on the environment. Critics argue that unethical tour operators wanting to take advantage of the trendy eco-tourism market print brochures that espouse the ethics of eco-tourism and show familiar emblems of green frogs and crocodiles to promote themselves but do little else. If such operators are not held accountable, the industry will not survive. Open and honest eco-tourism marketing, as well as world-recognized accreditation, must be endorsed and implemented. The sheer volume of tourists wanting to visit unique, unspoiled environments is also a cause for concern. Evidence of the need to restrict the number of visitors to sensitive areas exists in many eco-tourist attractions already. Hikers and bushwalkers in Mount Kenya National Park have caused damage by straying from set trails and leaving food scraps behind. The number of Orca whales visiting Canada has declined in recent migratory seasons, as the restrictions placed on whale-watching boats and organizers are thought to be inadequate.
Section E
Eco-tourism does not guarantee sustainable tourism and it should not be viewed as a complete cure for the problems that have beset tourism. Until all stakeholders agree to a definition of eco-tourism, insist that ecotourism operators abide by a strict code of ethics and carefully monitor the impact of eco-tourism (and all tourism), fragile ecosystems will continue to be besieged by tourists. There must be an educational program to promote ecologically-sustainable tourism across the board so that the underlying principle in ALL forms of tourism is the management of resources. Eco-tourism can bring wealth to areas where there is nothing else but natural attractions. The reasons for visiting the Galapagos Islands in Ecuador can only be explained by an interest in nature itself. The subsequent tourist dollars, if re-injected into the community, can mean the survival of such habitats. Licenses and entry fees to some sites have, in many cases, replaced government funding as their source of income. Countries as diverse as Australia, New Zealand, Costa Rica and Kenya are developing strategies to identify and cope with the constraints that inevitably come with a long-term vision of sustainable tourism. Eco-tourism has played an important role in developing an awareness for sustainable tourism practices but governments, tourist agencies, and operators must be willing to join forces with eco-tourists to ensure that natural attractions are protected from their popularity.
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The Cacao: A Sweet history
A. Chapter 1
Most people today think of chocolate as something sweet to eat or drink that can be easily found in stores around the world. It might surprise you that chocolate was once highly treasured. The tasty secret of the cacao (Kah Kow) tree was discovered 2,000 years ago in the tropical rainforests of the Americas. The story of how chocolate grew from a local Mesoamerican beverage into a global sweet encompasses many cultures and continents.
B. Chapter 2
Historians believe the Maya people of Central America first learned to farm cacao plants around two thousand years ago. The Maya took cacao trees from the rainforests and grew them in their gardens. They cooked cacao seeds, then crushed them into a soft paste. They mixed the paste with water and flavorful spices to make an unsweetened chocolate drink. The Maya poured the chocolate drink back and forth between two containers so that the liquid would have a layer of bubbles or foam.
Cacao and chocolate were an important part of Maya culture. There are often images of cacao plants on Maya buildings and art objects. Ruling families drank chocolate at special ceremonies. And, even poorer members of society could enjoy the drink once in a while. Historians believe that cacao seeds were also used in marriage ceremonies as a sign of the union between a husband and a wife.
The Aztec culture in current-day Mexico also prized chocolate. But, cacao plants could not grow in the area where the Aztecs lived. So, they traded to get cacao. They even used cacao seeds as a form of money to pay taxes. Chocolate also played a special role in both Maya and Aztec royal and religious events. Priests presented cacao seeds and offerings to the gods and served chocolate drinks during sacred ceremonies. Only the very wealthy in Aztec societies could afford to drink chocolate because cacao was so valuable. The Aztec ruler Montezuma was believed to drink fifty cups of chocolate every day. Some experts believe the word for chocolate came from the Aztec word “xocolatl” which in the Nahuatl language means “bitter water.” Others believe the word “chocolate” was created by combining Mayan and Nahuatl words.
C. Chapter 3
The explorer Christopher Columbus brought cacao seeds to Spain after his trip to Central America in 1502. But it was the Spanish explorer Hernando Cortes who understood that chocolate could be a valuable investment. In 1519, Cortes arrived in current-day Mexico. He believed the chocolate drink would become popular with Spaniards. After the Spanish soldiers defeated the Aztec empire, they were able to seize the supplies of cacao and send them home. Spain later began planting cacao in its colonies in the Americas in order to satisfy the large demand for chocolate. The wealthy people of Spain first enjoyed a sweetened version of chocolate drink. Later, the popularity of the drink spread throughout Europe. The English, Dutch and French began to plant cacao trees in their own colonies. Chocolate remained a drink that only wealthy people could afford to drink until the eighteenth century. During the period known as the Industrial Revolution, new technologies helped make chocolate less costly to produce.
D. Chapter 4
Farmers grow cacao trees in many countries in Africa, Central and South America. The trees grow in the shady areas of the rainforests near the Earth’s equator. But these trees can be difficult to grow. They require an exact amount of water, warmth, soil and protection. After about five years, cacao trees start producing large fruits called pods, which grow near the trunk of the tree. The seeds inside the pods are harvested to make chocolate. There are several kinds of cacao trees. Most of the world’s chocolate is made from the seed of the forastero tree. But farmers can also grow criollo or trinitario cacao plants.
Cacao trees grown on farms are much more easily threatened by diseases and insects than wild trees. Growing cacao is very hard work for farmers. They sell their harvest on a futures market. This means that economic conditions beyond their control can affect the amount of money they will earn. Today, chocolate industry officials, activists, and scientists are working with farmers. They are trying to make sure that cacao can be grown in a way that is fair to the timers and safer for the environment.
E. Chapter 5
To become chocolate, cacao seeds go through a long production process in a factory. Workers must sort, clean and cook the seeds. Then they break off the covering of the seeds so that only the inside fruit, or nibs, remain. Workers crush the nibs into a soft substance called chocolate liquor. This gets separated into cocoa solids and fat called cocoa butter. Chocolate makers have their own special recipes in which they combine chocolate liquor with exact amounts of sugar, milk and cocoa fat. They finely crush this “crumb” mixture in order to make it smooth. The mixture then goes through two more processes before it is shaped into a mold form.
Chocolate making is big business. The market value of the yearly cacao crop around the world is more than five billion dollars. Chocolate is especially popular in Europe and the United States. For example, in 2005, the United States bought 1.4 billion dollars worth of cocoa products. Each year, Americans eat an average of more than five kilograms of chocolate per person. Speciality shops that sell costly chocolates are also very popular. Many offer chocolate lovers the chance to taste chocolates grown in different areas of the world.
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