Category Science

How to determine if mosquitoes are ready to feed?

Mosquitoes buzzed around even when dinosaurs roamed the earth. By sucking blood and carrying parasites of crippling diseases, these creatures have ravaged human populations, especially in Africa. Mosquito bites have caused the death and disability of millions of people, ruining the economy of some countries:

Weaponized

Mosquitoes have been used as a biological weapon during wars. According to Winegard, the Nazis purposely re-flooded the Pontine Marshes around Rome and Naples in Italy to reintroduce mosquitoes, and they spread malaria in that part of Italy during World War II. The soldiers fighting the Nazis got malaria and had to be sent back.

With all the science and technology we have now, why are we not eradicating mosquitoes?

Here is why:

They’re everywhere

Mosquitoes are everywhere – in swamps, forests, fields and homes – 110 trillion of them. They are global, and have been around for 100 million years. They are great survivors, “masters of evolutionary adaptation.” They are resilient, which means they can adapt to different weather conditions and terrains. They withstood “global showers” of DDT spray, and five types of mosquitoes are now immune to this pesticide. We all have defences in our body against disease. In the same way, mosquitoes have developed immunity to survive our attempts to kill them off.

Untiring work

Still, a lot of work has been done to tackle this relentless insect. Funding is available for research on mosquito-borne disease. Mosquito nets are given out in large numbers to people. Insecticides and malaria drugs are distributed in counties that cannot afford them. Doctors say death from malaria, the major disease caused by mosquitoes, has decreased across the world. However, there is an increase in the incidence of Zika, West Nile, and dengue.

Governments are low trying biological control of mosquitoes. This is to avoid use of pesticides. In this method, fish are bred in ponds where mosquitoes lay eggs. The fish eat the larvae. There are also plants that kill mosquito larvae. But these have had only limited success in keeping down mosquito numbers.

Climate crisis

Mosquitoes thrive when we create the right environment for them – by rearing animals and plants close to our homes, cutting down trees, letting water stagnate and keeping sewage channels open. Climate change, which is now a serious crisis, also helps breed mosquitoes. “Increased temperatures mean a longer breeding season for mosquitoes,” said Winegard in an interview.

“Canada has seen a 10% increase in mosquito-borne disease in the last 20 years. In the southern US, we’ve seen domestic cases of Zika, chikungunya, and even dengue in the last 10 years. So if temperatures rise around the planet, which increases the risk of spreading disease.”

 

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Why is the mosquito deadly?

The mosquito transmits or carries more diseases than any other insect. The six major ones spread by it are: malaria, dengue fever, chikungunya, zika fever, lymphatic filariasis and Japanese encephalitis.

Different species of the mosquito cause different illnesses. Research into human civilisation shows that mosquito-borne diseases throughout history have killed more people than man-made weapons.

In the book: The Mosquito: A Human History of Our Deadliest Predator, historian Timothy Winegard gives us this startling fact: over the course of 200,000 years, 108 billion people have lived on Earth. Of these, 52 billion have been killed by mosquitoes. Since 2000, an average of 2 million people have died due to diseases caused by mosquitoes. And so, it is safe to sat, the insect has had a disastrous effect on our civilisation.

 

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WHICH ANIMALS LIVE IN RAINFORESTS?

Tropical rainforests are home to an incredible range of animal life. Over half of the world’s known species exist in the Amazon rainforest alone. Colourful birds, such as toucans, parrots and macaws, live alongside gorillas or other primates, while tigers, pumas and wolves may roam among countless poisonous snakes and insects.

It is said that a single hectare (about two and half acres) of rainforest can contain up to 1500 species of plants plus 750 species of trees. It is this wealth of plant life that attracts and sustains an amazing collection of animals. For example, one in five of all bird species are found in the Amazon rainforest.

Mammals such as Orangutans (in Asia), Gorillas (Africa), Jaguars (South America) and sloths (Central and South America) all call the rainforest home. Sloths spend most of their time in the trees. Their hooked claws and long arms allow them to spend most of their time hanging upside down! Sloths are herbivores and due to their slow movement and metabolism it can take them up to a month to digest their food! Reptiles such as Anacondas, the Emerald Boa Constrictor and the Gaboon Viper slither through the trees and on the forest floor. Insects including cutter ants, tarantulas, scorpions, butterflies and beetles rummage on the forest floor. Amphibians such as frogs and toads live in trees or near bodies of water on the forest floor. Fish including the piranha, Amazonian catfish, fresh water dolphins and stingray inhabit the rivers that run through the rainforests.

Because there are so many animals in the rainforest there is a lot of competition for sunlight, food and space. Animals therefore have to adapt to the environment.

Some animals use camouflage to hide from predators and some predators use camouflage to help them hunt for food. Their colouring or patterned skin help them disappear into the rainforest, blending into the colour of the bark or leaves.

Some animals don’t hide, some use their colouring to warn potential predators away. The poison dart frog is a good example, they may be small but they are one of nature’s most toxic and dangerous creatures. Some local people put the frog’s poisonous toxins on the tips of their blowpipe darts to kill small prey which they then eat.

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WHAT IS SPECIAL ABOUT CORAL REEFS?

Coral reefs are special areas of coastline made from living things. They grow in areas where the water is particularly warm, clear and shallow. Tiny sea animals cling to the coastline. When they die, they create limestone skeletons to which more creatures attach themselves. As these die, more creatures cling on, and the process continues. Coral reefs are among the strongest structures on Earth, as well as making up some of the world’s most beautiful coastlines.

Coral reefs are communities of hundreds of thousands of tiny animals called coral polyps. They grow in sunlit shallows of warm clear water. The reefs are built up as new corals attach atop the skeletons of dead animals. These coral reefs play a fundamental role in protecting coastlines from erosion and contribute to the formation of white sandy beaches.   Found around coastlines in the tropics, coral reefs provide homes for about a third of all fish species on Earth.

The coral species that are the reef’s foundation have very specific needs for light, temperature, salinity and oxygen.   They are easily damaged or killed.  Reefs are sensitive to unusually warm waters caused by global warming.  They are smothered by erosion from deforestation and dredging of rivers and bays.   They are blown up by fishers using dynamite, poisoned by collectors working for the aquarium trade and inadvertently damaged by boaters and scuba divers who stand on reefs or inadvertently hit them with fins or dangling equipment, breaking off pieces of the fragile coral. Damage from anchors and accidental boat groundings is a severe problem.

Cyanide and other toxins are used to stun reef fish so they can be captured alive to be sent to fish markets as aquarium specimens. The accumulation of poisons is killing the reefs. Improvements in the ability to keep corals alive has spurred a worldwide demand for live corals for aquariums.

Recently, scientists have become alarmed by increased occurrences of “coral bleaching”.

In many parts of the world the reefs are turning white and dying.
Coral gets its beautiful colors from the algae that live within.  This algae produce oxygen and sugars for the coral polyps to eat. The coral, in turn produces carbon dioxide and nitrogen which enhances algae growth.

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DO BEACHES ALWAYS REMAIN THE SAME?

Beaches are changing all the time. Shingle and sand on beaches is constantly shifted around by the action of the wind and waves —a process known as longshore drift. The same beach may be made of pebbles at one time of the year, yet be sandy a few months later.

Beaches are constantly changing. Tides and weather can alter beaches every day, bringing new materials and taking away others. Beaches also change seasonally. During the winter, storm winds toss sand into the air. This can sometimes erode beaches and create sandbars. Sandbars are narrow, exposed areas of sand and sediment just off the beach. During the summer, waves retrieve sand from sandbars and build the beach back up again. These seasonal changes cause beaches to be wider and have a gentle slope in the summer, and be narrower and steeper in the winter.

Most beach materials are the products of weathering and erosion. Over many years, water and wind wear away at the land. The continual action of waves beating against a rocky cliff, for example, may cause some rocks to come loose. Huge boulders can be worn town to tiny grains of sand.

Beach materials may travel long distances, carried by wind and waves. As the tide comes in, for example, it deposits ocean sediment. This sediment may contain sand, shells, seaweed, even marine organisms like crabs or sea anemones. When the tide goes out, it takes some sediment with it.

Every beach has a beach profile. A beach profile describes the landscape of the beach, both above the water and below it. Beaches can be warm, and rich in vegetation such as palm or mangrove trees. Beaches can also be barren desert coastlines. Other beaches are cold and rocky, while beaches in the Arctic and Antarctic are frozen almost all year.

The area above the water, including the intertidal zone, is known as the beach berm. Beach berm can include vegetation, such as trees, shrubs, or grasses. The most familiar characteristic of a beach berm is its type of sand or rock.

Sandy

Most beach sand comes from several different sources. Some sand may be eroded bits of a rocky reef just offshore. Others may be eroded rock from nearby cliffs. Pensacola Beach, in the U.S. state of Florida, for instance, has white, sandy beaches. Some sand is eroded from rocks and minerals in the Gulf of Mexico. Most sand, however, is made of tiny particles of weathered quartz from the Appalachian Mountains, hundreds of kilometers away.

Rocky

Some beach berms are not sandy at all. They are covered with flat pebbles called shingles or rounded rocks known as cobbles. Such beaches are common along the coasts of the British Isles. Hastings Beach, a shingle beach on the southern coast of England, has been a dock for fishing boats for more than a thousand years.

A storm beach is a type of shingle beach that is often hit by heavy storms. Strong waves and winds batter storm beaches into narrow, steep landforms. The shingles on storm beaches are usually small near the water and large at the highest elevation.

Other types of beaches

Some beaches, called barrier beaches, protect the mainland from the battering of ocean waves. These beaches may lie at the heads of islands called barrier islands. Many barrier beaches and barrier islands stretch along the Atlantic and Gulf coasts of the United States. These narrow beaches form barriers between the open ocean and protected harbors, lagoons, and sounds.

Beaches near rivers are often muddy or soft. Soil and sediment from the river is carried to the river’s mouth, sometimes creating a fertile beach. Hoi An, Vietnam, is an ancient town that sits on the estuary of the Thu Bon River and the South China Sea. Hoi An’s soft beaches serve as resort and tourist center.

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CAN COASTLINES BE PROTECTED FROM THE SEA?

It is possible to prevent or, at least, slow down the erosion of some coastlines. Groynes help to prevent longshore drift; while trees and grasses can be specially planted to stop sand dunes being blown away. Sea walls help to prevent coastal erosion and protect low-lying areas from flooding.

As sea levels rise and coastal communities face the threat of erosion and flooding, coastal defence structures, often built with concrete, have become the norm in many parts of the world.

But these hard engineered structures, like seawalls, breakwaters and groynes, are both expensive and bad for the environment. Our team of University of Melbourne scientists is joining a growing number of international researchers looking at whether natural coastal defence structures could be a better option. We are trialling mussel reefs and mngrove forests in Melbourne’s Port Phillip Bay to see how well they protect our shorelines.

Natural coastlines have in-built coastal defence in the form of sand dunes and beaches, saltmarsh, mangroves, seagrass and kelp beds, and coral and shellfish reefs. These natural structures can reduce the height of waves as they approach the shore and trap sediment, increasing the height of the land relative to sea level. This reduces flooding and erosion. Mussel reefs and mangrove forests are particularly important in Port Phillip because they are native habitats that have suffered significant declines historically. We are creating the mussel reef from recycled shell and natural basalt rock, and we expect it to reduce wave height and promote accretion of the eroding foreshore.

For the mangrove forests we will use a ‘hybrid’ approach, which involves planting the mangroves within concrete cultivars that attenuate waves, accrete sediment and provide the right conditions for the forests to grow. Elsewhere, other natural habitats are being used to protect shorelines. For instance, in the United States, oyster reefs have been widely restored on the east coast to provide erosion control. Oysters need something hard to attach to, and lots of creative reef designs have been engineered to replace lost habitats and enhance oyster populations.

In contrast, artificial structures are expensive to build and maintain and cause significant ecological damage. In particular, they lead to a loss of biodiversity through the replacement of natural habitats and are often hotspots for invasive species.

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