Debate ranges on over how to solve the problem of global emissions of carbon dioxide from burning fossil fuels. A new study has shown that if we’re not careful, growing crops to turn into biofuels could spell disaster in the sea by worsening so-called ‘marine dead zones’ where wildlife is wiped out by depleted oxygen levels.
When fertilisers are applied to agriculture land – including onto biofuel crops – much of it washes into coastal waters where it triggers blooms of algae. The algae eventually die and sink to the sea floor where bacteria break them down, using up oxygen in the process.
Because of this, every year, a huge and growing area of sea become anoxic and unable to support life. In 2008, the dead zone in the northern Gulf of Mexico was more than 27,000 km2 – that’s over half the size of England.
Christine Costello and W. Michael Griffin and colleagues from Carnegie Mellon University and the University of Pittsburgh in the US, have developed a computer model of the Gulf of Mexico to predict what is likely to happen if more biofuels are planted – something that the US federal government are pushing for in at attempt to tackle climate change. The target is for 36 billion gallons of biofuels to be produced each year by 2022.
To meet this biofuel target, no matter what crops are planted – even grasses that need less fertiliser– it will lead to a massive increase in the amount of nitrates reaching the Gulf of Mexico and a worsening of the dead zone.
The authors point out various options for reducing the impacts of nutrient runoff from agricultural land, including planting strips of vegetation along riverbanks – so-called Vegetative Buffer Strips – as well as constructing areas of wetland and the very precise application of fertilisers.
If crop-based biofuels hold any hope as the sustainable green solution of the future, these are the sorts of things that need to be promoted.