Category Environtal Studies

How Dead Zone formed?

Dead ones generally occur near areas where heavy agricultural and industrial activity spill nutrients into the water. The excess nutrients, especially nitrogen and phosphorous, cause the rapid growth of microscopic algae called phytoplanktons. This phenomenon is called the nutrients, grow, die and sink to the bottom, where they are decomposed by bacteria. The bacteria inhale the dissolved oxygen in the water as they decompose the phytoplankton. This leads to the depletion of oxygen available to other marine life.

If the phytoplanktons are cyanobacteria, the problem is further intensified they are not consumed by zooplankton and fish. Hence they accumulate in water, leading to the expansion of dead zones. The bacterial degradation of their biomass consumes more oxygen in the water.

While nutrients run-off has been known for decades, researchers say that climate change is making the lack of oxygen worse. As more carbon dioxide is released enhancing the greenhouse effect much of the heat is absorbed by the oceans. In turn, this warmer water can hold less oxygen.

Stratification

The other worrying factor is the possible hindrance to replenishment of oxygen. This happens when the water is warmer than usual. Oxygen in the air and the surface usually gets dissolved in the water below by tides and winds. This helps restore the gas consumed by bacteria. When the temperature of the water is high, less dense water flowing into the ocean from rivers sits on top of salty dense water. This process is called stratification. A barrier is formed between the separated masses of water, hampering the replenishment process.

 

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What are Dead Zones?

Dead zones are low oxygen areas in the world’s oceans and lakes. A combination of physical, chemical and biological factors creates dead zones, with nutrient pollution being the major culprit. These nutrients come from the run-off of chemical fertilizers and wastewater.

Hypoxic zones can occur naturally, but scientists are concerned about the areas created or enhanced by human activity.  Excess nutrients that run off land or are piped as wastewater into rivers and coasts can stimulate an overgrowth of algae, which then sinks and decomposes in the water. The decomposition process consumes oxygen and depletes the supply available to healthy marine life.

Dead zones occur in many areas of the country, particularly along the East Coast, the Gulf of Mexico, and the Great Lakes, but there is no part of the country or the world that is immune. The second largest dead zone in the world is located in the U.S., in the northern Gulf of Mexico.

 

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Are our oceans going breathless?

Dissolved oxygen in water is essential for the survival of fish and other aquatic organisms. Levels that are too high or too low can harm aquatic life and affect water quality. There are regions in oceans across the globe where the concentration of dissolved oxygen can be so low that marine animals can suffocate and die, and as a result, these regions are often called dead zones. A new study by the conservation group the International Union for the Conservation of Nature (IUCN) has revealed that the number of dead zones has quadrupled in the last half-century – from only 45 in the 1960s to as many as 700.

Citing climate change and increase in nutrient pollution as the causes, the IUCN has warned that many species of fish, including sharks, tuna and marlin are at particular risk. These fishes are sensitive to low levels of the life-giving gas due to their large size and energy demands.

The report on ocean oxygen loss concluded that deoxygenation is already altering the balance of marine life to the detriment of species across the food chain. The biomes that supports about a fifth of the world’s current fish catch are formed by ocean currents usually bring oxygen-poor water to coastlines. So, these areas are especially vulnerable to even tiny variations in oxygen levels, it said.

On currently trends, oceans are expected to lose 3-4% of their oxygen globally by 2100. Most of that loss is predicated to be in the upper 1,000 mt – the richest part of the ocean for biodiversity.

 

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What is the role of climate change in Australia bushfires?

Over the last few decades, there has been a significant spike in the number of wildfires. Greenhouse gas emissions have led to an increase in global temperature. As warmer temperatures hasten evaporation, the land subsequently turns drier, enhancing the chances of wildfires.

A 2019 Australian government report on wildfires and climate change said human-caused climate change has resulted in more dangerous weather conditions for bushfires in recent decades for many regions of Australia.

 Heatwave and drought

Fire season in Australia is always dangerous. But conditions have been unusually severe this year. Australia is experiencing one of its worst droughts in decades. Meanwhile, a heatwave last December broke the record for highest nationwide average temperature, with some places sweltering under temperatures well above 40 degrees Celsius.

Fire season has changed

With climate change, weather conditions are growing more extreme, and for years, the fires have been starting earlier in the season and spreading with greater intensity in Australia. The fire season is starting earlier and is about two to four months longer, especially in south and east Australia. The normal peak fire season is later in summer, which is January and February. Australia is just entering its summer season, meaning the country could be months away from finding relief.

 

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What are the impacts on animals of Australian bushfires?

 Though it is estimated that nearly half-a-billion animals have been affected in one State alone, it is difficult to get the exact number until fires subside enough to allow surveys of the burned areas. Fires have been part of the Australian landscape for thousands of years. Many species and ecosystems have evolved to cope and later populate nearby unaffected land. But as climate change fuels longer five seasons and more frequent, intense fires, it could become increasingly difficult for animals to adapt newer escape strategies and for ecosystem to bounce back.

In the line of fire

Smaller mammals and reptiles can escape the blazes by burrowing underground or hiding in rocks.

But some are not good at coping heat or stress. Wombat, the small, stubby-legged marsupial, can’t run very fast or far. Kolas are particularly vulnerable to bushfires as their slow movement and tree-dwelling lifestyle make it difficult for them to escape. Koalas and kangaroos are primarily killed directly by the fires. In this season, nearly a third of all koalas in New South Wales have died and about a third of their habitat has been destroyed according to a government estimate.

Ecosystems are built on balance – once one element is thrown off, everything is affected. Even if animals don’t die from the flames or smoke, they would eventually do from the fire’s aftermath. After their habitat is destructed, there will be no shelter or food left to survive on. These animals’ recovery depends not only on their population size, but also on the condition of their habitat.

 

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What is wildfire?

An uncontrolled fire in an area of combustible vegetation that spreads quickly, wiping out large areas of land is called a wildfire. A wildfire can also be termed a forest fire, a grass fire, a peat fire or a bushfire depending on the type of vegetation.

During summer, when there is no rain for months, the forests become littered with dry leaves and twigs, which could burst into flames ignited by the slightest spark.

Natural causes: Lightening is the most common cause of bushfire. There are three conditions for a bushfire to spread – fuel, oxygen and a heat source. In the forest, anything that is flammable is a fuel. This includes tall, dry grass, bushes and trees. High temperature, drought and dry vegetation are a perfect combination for igniting a forest fire.

Human-made disaster: Human neglect such as downed powerlines, sparks from tools or forest machinery, abandoned campfires and discarded cigarette butts can spark fires. People also tend to clear forests by setting them on fire to pave way for cultivation. Sometimes they set fire to scare away wild animals and the fire could spread and turn disastrous.

In Australia:

Summer is the season of fire in Australia with hot, dry weather making it easy for blazes to start and spread. Most of the time, it is natural causes such as lightning that trigger a fire, but sometimes human are also to blame. New South Wales police have charged at least 24 people with deliberately starting bushfires, and have taken legal action against 183 people for fire-related offences since November, according to reports.

 

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