Thursday, June 16, 2011

A world without beaches?

Having been reading various papers and reports on climate change for some time now, I thought I had a pretty good grasp on the range of negative effects associated with the unprecedented rate of change our actions are causing in the planet's atmosphere and oceans: higher temperatures, changing patterns of precipitation, more frequent heat waves and bushfires, more intense storms and floods, habitat destruction, biodiversity decline, cryosphere melt, reduced agricultural yields, increased water stress, increased area affected by drought at any one time, ocean acidification (which is not directly related to climate, but has the same cause: rising carbon dioxide levels), modified vector borne disease spread (such as dengue and malaria), exacerbation of respiratory health issues associated with ground-level ozone (smog), human migration patterns (refugees), desertification, shifting ocean currents, warming oceans, coral bleaching and mortality, poleward movement of the tropics, destabilisation of permafrost, shifts in the timing of annual events such as flowering, hibernations, migrations and peak river flows, sea level rise and the consequent threat to infrastructure during storm surges as well as salination of coastal water tables. All these I've read a fair bit about over the last couple of years. But only recently I have come across an implication that I hadn't heard before, one with a high visual and emotional impact for many people, but which, as far as I can tell, is not yet widely known.

Much has been said about sea level rise, and I don't intend to give a full account here. But quite apart from the risk of flooding, rising seas mean coastal erosion. I had not grasped how significant this could be. A rule of thumb used by some researchers is that, roughly speaking, for each centimetre of sea level rise, coasts will erode by one metre. When we are looking at a likely sea level rise between 50 and 200 centimetres by 2100 (and continuing thereafter for some time), you quickly get a sense of the scale of this particular issue. Sea defences can be built to minimise this impact, but they are only partially or temporarily effective (or extremely expensive), especially against the scale of change we are looking at.

Where the public at large are likely to particularly notice this, especially in Australia, is in its effect on beaches, many of which are likely to be progressively stripped of sand over the coming decades. The processes involved are complex and only partially understood, and there may be much local variation in how sea level rise affects coastal areas. Nonetheless, loss of sand is already a major (and costly) headache for many beaches and the best estimates are that this will generally get worse.

Many of us are likely to live to see a world virtually free of summer Arctic sea ice; our children may see the last of the great coral reefs die; our grandchildren may need an explanation of what a sandy beach was.

13 comments:

besideourselves said...

Does that mean less people at the beach and more reef-breaks?

(I'm working hard at finding a 'bright-side' here)

Jeremy said...

Then I suspect it's only a matter of time before there are groynes on Bondi. (we should find a new name for those things, honestly) More artificial protected beaches like the ones at the old British seaside towns, and fewer wild and natural ones.

One Salient Oversight said...

Rising sea levels will cause erosion but in many cases this will result in beaches being created or at least simply moving up over time.

I visited Lake Pedder here in Tasmania a few months ago. As you know, the lake was once famed for its pearl-white sandy beaches. Now that it has been dammed and covered with water (i think dozens of metres above the original beach) the beach can't be seen. However what has transpired is the creation of pearly-white beaches at the new water level.

Since sea level rise won't occur at the same speed as the Damming of Lake Pedder (which increased its height by dozens of metres over a 2-3 year period) you're probably going to simply see beaches rise with the sea level.

craigbenno1 said...

I'm a bit sceptical about this Byron... :(

Is there any evidence that suggests raising sea levels from the climatic changes from aeons past?

In fact historians tell me that some million years ago there was a huge inland sea in the middle of Australia... if climate change is really real - perhaps its just swinging back on its pendulum...

Btw what did cause that huge inland sea to dry up - surely we can't blame the human race for that one?

Byron Smith said...

OSO - Good point. As I said, I have not yet read a great deal about this topic and so hope that you may be right. However, from what I've picked up so far, in terms of beach sand erosion, there will be some winners and more than a few losers. Beaches are pretty much always on the move, but the pace of change is going to continue to increase.

Craig - Because fires have happened for millions of years we don't discount obvious cases of arson today. Natural climate variations are relatively well understood and there are all kinds of reasons that the current changes are likely to be primarily caused by human actions.

One Salient Oversight said...

Is there any evidence that suggests raising sea levels from the climatic changes from aeons past?

Yes. Plenty. Let me give you one example.

I live in Tasmania now. We have an animal here called the Tasmanian Devil. Remains of this animal have been found on the mainland. Why wasn't the TD found long dead on the mainland but alive in Tasmania.

It's because of two things: Dingoes and rising sea levels. The land bridge between Tasmania and the Mainland was covered over long, long ago, cutting off the Tasmanian Devils from their Mainland relatives.

A few thousand years ago Dingoes were brought to Australia. They naturally became a predator for many animals, and the mainland Devils were made extinct as a result. Yet Bass Strait prevented the Dingoes from crossing into Tas.

byron smith said...

Guardian: Italy's elite dismayed at disappearing beaches.

Not every eroding beach is linked to sea level rise, and as OSO points out, it may well be that not every beach is threatened by sea level rise, but I don't think I'm going out on a limb to make the more moderate claim that an increasing number of beaches will suffer coastal erosion under increasing sea levels. I'll keep an eye out for more on this topic.

byron smith said...

DD: Erosion on the US west coast.

byron smith said...

CC: Coastal erosion in Georgia.

byron smith said...

It seems that one of the critical factors determining the effects of coastal erosion is the presence or absence of hard infrastructure (esp. sea walls and the like). Places that don't have them are more likely to see the beach gradually retreat inland. Places with them are in more trouble and some/many could see beaches shrink, shift or even disappear.

byron smith said...

Reuters: California counts the cost of coastal erosion threat.

byron smith said...

NYT: Hawaii's beaches are in retreat.

byron smith said...

PhysOrg: Iconic beach resorts may not survive sea level rises.

Key takeaway: beaches can survive SLR as long as they are allowed to move. It is when a moving beach meets a concrete wall (built to protect beachside properties) that beaches are lost.