Sunday, September 2, 2012

Enriching The Soil

Good article from the BBC about the worldwide use of fertilizers (or 'fertilsers') for farming:
Directly or indirectly, plants are the making of us. We rely on plants because we can’t metabolise the nitrogen that makes up four-fifths of the air we breathe. Nitrogen is a vital constituent of all proteins as well as other important molecules, including DNA, but we can only use nitrogen once it has been broken down and combined into a salt molecule, such as potassium nitrate, for example.

So for thousands of years, humans have come up with ingenious ways of replacing the nitrogen – and other essential nutrients such as phosphorous – they have taken from the soil.

Farmers left stalks and silage in the fields to rot down, and added whatever other organic material they could, including animal and human excrement. As populations grew in Europe and the US, nineteenth-century scientists found precious useable nitrogen supplies in South America, in the form of vast quantities of guano – bird droppings – which indigenous people had been using for centuries as a soil enricher. This discovery, and of the nearby saltpetre (potassium nitrate) mines, generated enormous interest in Europe and the United States. Trainlines were constructed at great expense through the desert to export the valuable materials, and the War of the Pacific kicked off between the guano- and saltpetre-rich nations of Peru, Bolivia and Chile. Britain supported Chile, enabling it to win most of the guano and saltpetre area and Bolivia’s entire coastline in the process.

Come the turn of the last century, though, the need for guano was replaced by a revolutionary idea. The German chemist Fritz Haber invented a way of converting the nitrogen in air into liquid ammonia (NH3). The era of artificial fertilisers was born.

The effect on crop production and hence population growth was immediate. The number of humans that could be fed from 1 hectare of land (2.47 acres) rose from 1.9 to 4.3. Half of the protein in our bodies now comes from ammonia made in the Haber process. (Unfortunately, the same reaction also leads to the production of powerful explosives, which have been responsible for the deaths of some 150 million people.) Billions of people owe their daily bread, rice or potatoes to artificial fertilisers. And fertilisers formed the backbone of the Green Revolution across Asia and South America, which dramatically improved yields and has lifted millions out of starvation over the past 40 years.

But only 17% of the nitrogen used in fertilisers ends up in our food; the rest ends up in soils and water. And that’s where the greatest problem lies, because nitrogen is also a superb fertiliser of algae and bacteria. Fertiliser pollution in lakes and the ocean causes massive blooms of algae, which use up the oxygen dissolved in the water, suffocating other species. The vast blooms of red or green algae cause dead zones for kilometres, with the associated stench.

Ten times more nitrogen is used to produce food than humans consume as protein, and not all the nitrogen in the food we eat is even used by our bodies – the excess enters the environment through human waste. Most people require only 2g (0.07 ounces) of nitrogen a day, but the average American consumes 13g (0.46 ounces) daily, mainly in animal products, which are fed on fertilised crops.

Over-use of fertilisers is a particular problem in China, where whole river systems are polluted and the soils degraded by intensive farming. But safeguards in Europe, including using only a small amount of fertiliser where needed, and providing catchment reed beds that filter out any runoff before it enters the river, have greatly reduced the problem there.

However, local fertiliser use has a global impact. Producing fertilisers also pollutes the atmosphere with climate-altering greenhouse gases. The Haber reaction requires burning fossil fuels, which emit carbon dioxide. And other potent greenhouse gases, including nitrous oxide, are also released while making or using fertiliser. Transporting fertiliser also releases significant carbon emissions, making it a dirty industry.
Fertilisers: Enriching the world’s soil (BBC) . I wonder, are we truly enriching the soil, as the title of the article implies, or are we strip-mining it for temporary benefit? Also from the BBC:
Some 10,000 years ago, at the beginning of the Holocene geological age, there were only around five million of us on the planet. Although humans had a significant impact on the natural world – by using fires to clear forestry or hunting large mammals to extinction – their effects were localised.

Boy, have things changed. In 1900, there were 1.6 billion of us; by 2000 the global population had shot up to 6.1 billion. Last year, we passed the seven billion mark, and best estimates have us reaching the nine billion mark before 2050.

The sheer number of people has profoundly changed the global landscape, as we convert vast tracts of wild vegetation to agricultural or grazing areas, for example. Fishing on an industrial scale to provide for billions has dramatically altered marine diversity. Individual farmers breeding livestock or keeping chickens, when multiplied by millions, have caused biodiversity changes in which more than 90% of the weight of all terrestrial vertebrates is now made up of humans and the animals we've domesticated. The quest for resources to supply us all with materials and the trappings of life has depleted the forests, polluted rivers and soils and even carved the tops of mountains. And the fuels used by each of us for energy have produced combined emissions that are already altering the planet's climate.

By 2050, it is estimated that we could triple our resource consumption to a whopping 140 billion tonnes of minerals, ores, fossil fuels and biomass per year. Our food requirement alone is expected to double by then.

Is our ever-increasing human population propelling us to our doom? Is there a limit to how many people can be sustained on a finite planet – and, if so, have we already passed it?
Are we facing population overload? Unfortunately, these articles tend to state the problems very well, but the solutions seem unrealistic and unsatisfying. This paragraph particularly stood out:
But with over half of the world's land already used for agriculture, do we really want to plough the rest? In the next four decades we're going to have to produce more food than we have during the last 10,000 years in soils that are degraded, marginal lands and under the difficult conditions of climate change.

1 comment:

  1. Chilean saltpetre is sodium nitrate, not potassium nitrate. Terribly sorry about that.


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