Archive | February, 2013

The threat posed to agriculture

19 Feb

One of the dominant ideas supported by the long term linear view of climate change – the nice gentle shifts envisaged by the IPCC reports – is that there will be plenty of time to adapt and that our agricultural regions will gradually move towards the polar regions.

Unfortunately, this viewpoint is scientifically out of date and neglects a lot of complicating factors in agriculture.

The reason the viewpoint is scientifically out of date is that an emerging area in climate science is studying the link between climate change and changing weather. It turns out that we can’t expect nice gentle changes (and this has been known to paleoclimatologists for a lot longer than modellers) but there is a much higher than originally expected risk of sudden and abrupt transitions in how the earth system operates.

We are already seeing the fingerprint of climate change in an increasing incidence of extreme weather – some of it driven by the rapid (abrupt, even) loss of albedo from the Arctic as sea ice and land based snowpack melt faster and sooner than usual. This reduces the thermal gradient bewteen the polar and adjacent regions of the planet – altering the behaviour of the jet stream. In most seasons of the year the movement of the weather systems is slowed, the track of the jet stream tends to be amplified and there is a significantly higher chance of blocking events forming which reinforce the weather and give rise to more extreme events.

This is because many extreme types of weather become self reinforcing through simple persistence. A few days of heavy rain may just be a normal event – but continue the same rain for a few weeks and the ground becomes saturated and flooding becomes much more of a problem than would be implied simply by the extension in rainfall duration.

Likewise warm and dry conditions can lead to dramatic heatwaves if they persist for longer as evaporation dries out the soil. This evaporation absorbs energy and in doing so acts to limit temperature rise. Once the amount of moisture available to absorb thermal energy in this way is too low – the temperature is free to soar.

Evidence is also mounting that other types of extreme weather are increasing although the drivers behind this are not well understood in all cases. It should also be noted that it takes time and effort to identify clear signals in extreme weather as by definition we are looking for extreme events. One recent study that effectively did this with respect to heatwaves over the surface of the planet was done by Hansen – concluding that the incidence of extreme heat had risen (already – in the present day) from <1% of the surface of the planet to around 10% – a very significant change.

Extreme weather is therefore the first and most currently obvious problem facing farmers. There are several key facets to this problem. The first is that a food crop is vulnerable through the entire growing season to extreme weather and only one extreme event can be enough to devastate the yield of the crop. Too much or too little heat or moisture at the wrong times – or simply a late frost following a mild start to spring – can cause very extensive loss of yield..

Additionally it becomes ever harder for farmers to plan their crop as the certainty over the conditions they expect diminishes. This statistically reduces yield as more farmers are likely to plant the wrong crops for the conditions they face.

The idea of adapation is often raised with respect to agriculture. This idea is flawed for several reasons. One reason is that we have had ten thousand years to evolve our food crops to our current ecosystem. It simply isn’t as easy as people think to grow crops in other regions.

Some crops are dependent on day length to drive their activity – clearly moving such a plant too far from it’s natural habitat to try to find the right climatic conditions in other respects will impair or inhibit it’s performance. Some crops depend upon particular insect pollinators or other elements of the ecosystem that are much harder to transplant arbitarily. Different types of soil favour different crops – and many other specific factors that affect viability at any given location.

As local ecosystems are thrown out of balance there is a very high risk of invasive pests and diseases proliferating. The rise of the pine beetle is one example of this – but other pests such as locusts will find themselves able to enter new habitats where previously they would not have survived.

It also seems likely that the logistics of agriculture will become virtually impossible – both for the practice of and for adaptation. Once the rate of change becomes too high and existing agricultural practises start to experience widespread failure the loss of social cohesion and the rise of conflict and famine will create a situation where it becomes almost impossible to either practice agriculture or to source alternate seeds to try in the new conditions being experienced.

As we enter a period of increasingly abrupt climate change this becomes an ever more probable issue.

Finally – when the dust settles and the climate starts to settle down – however many decades (or centuries) into the future – it is likely that the earth system will be very different to what we are familiar with now. Even now we are receiving a glimpse into new conditions where we don’t have any direct analog for what we are used to (and our crops are also used to). We see this in the quantity of records being broken by extreme events. In the course of the next few years we are likely to see – for what is most likely the first time in our evolutionary history – an ice free Arctic during the summer.

Over the next few years after that the albedo driven positive feedback all but ensures that the ice free period will be spanning a significant portion of the year. Therefore it is not very far into the future when we can no longer presume upon the earth system – and agriculture – operating as we have known it for the last ten thousand years. This is a very fundamental change and perhaps difficult for most people to intellectually comprehend.

For our work in the Civilisation Continuity Group this represents a very serious challenge – especially as we look into the longer term future. Agriculture is the basis of our civilisation – without it the number of people the land can support is necessarily low and it is unlikely for those people to form substantial settlements – another key foundation for an advanced civilisation as nomads must carry their whole world with them as they move and this is a limiting factor.

It is therefore necessary that some agricultural technology be preserved by some people somewhere for our species to have a chance at an ultimately better future again.

Prudence dictactes that we should not underestimate the difficulties of even this apparently simple task in the future that rushes towards us.