Does the 80/20 rule apply for reducing sediment delivery to streams?
Blog post.
Tom Mackay-Smith and Raphael Spiekermann
7/25/20242 min read
The 80/20 rule is a principle that pops up again and again.
It describes how a small proportion of inputs, causes or effort are often responsible for a disproportionately large amount of outputs, consequences and results.
• When first describing the rule, Italian economist Vilfredo Pareto found that 20% of the population owned 80% of the land in 1897 (1).
• One study found that 80% of birds seen are from 20% of species (2).
• In the Harvard library, 65% of the books are by 3% of the poets (1).
The rule can then be used for making improvements in how we do things. For instance, IBM discovered that 80% of a computer's time is spent executing 20% of its operating code (1). IBM then focused on making this 20% of operating code easier to find and more user friendly making their computers more efficient.
How does this relate to land management?
For their research, Raphael and his team also did some scenario modelling that estimated sediment reductions to streams under two planting strategies involving 50 farms in the Wairarapa region:
One assumed that poplars at 15 m x 15 m spacings were planted on areas that had a high chance of slipping and also a high chance of being connected to streams.
The other assumed that poplars were planted across the whole extent of the farms at 15 m spacings.
The first targeted scenario was only 6.5% of the land area of the farms (2,400 ha of 37,000 ha in total). However, it achieved 60% of the sediment reduction from landslides compared to the scenario where all the farms were planted in poplar trees.
This data suggests that the real problem in terms sediment delivery to streams from landslides occurs on only a small part of the farm. If these areas are targeted, then it could have a massive impact on reducing sediment delivery to streams via landslides.
Raphael also broke down the cost to reduce sediment delivery via landslides and found that the targeted strategy was 10x more cost-effective.
You can find the full paper for the research through this link, and we have produced a video summarizing the research here.
Koch, R. Welcome to the 80/20 principle. in The 80/20 Principle: Achieve More with Less (nb, 2022).
Rispoli, F. J., Zeng, S., Green, T. & Higbie, J. Even Birds Follow Pareto’s 80–20 Rule. Significance 11, 37–38 (2014).
