Forest Cover Tipping Points

There’s an interesting discussion of forest tipping points in a new paper in Science: Global Resilience of Tropical Forest and Savanna to Critical Transitions Marina Hirota, Milena Holmgren, Egbert H. Van Nes, Marten Scheffer It has been suggested that tropical forest and savanna could represent alternative stable states, implying critical transitions at tipping points in … Continue reading “Forest Cover Tipping Points”

Forest Cover Tipping Points

This is a model of forest stability and transitions, inspired by: Global Resilience of Tropical Forest and Savanna to Critical Transitions Marina Hirota, Milena Holmgren, Egbert H. Van Nes, Marten Scheffer It has been suggested that tropical forest and savanna could represent alternative stable states, implying critical transitions at tipping points in response to altered … Continue reading “Forest Cover Tipping Points”

Tipping points

The concept of tipping points is powerful, but sometimes a bit muddled. Things that get described as tipping points often sound to me like mere dramatic events or nonlinear effects, simple thermodynamic irreversibilities, or exponential signals emerging unexpectedly from noise. These may play a role in tipping points, and lead to surprises, but I don’t … Continue reading “Tipping points”

Feedback and project schedule performance

Yasaman Jalili and David Ford look take a deeper look at project model dynamics in the January System Dynamics Review. An excerpt: Quantifying the impacts of rework, schedule pressure, and ripple effect loops on project schedule performance Schedule performance is often critical to construction project success. But many times projects experience large unforeseen delays and … Continue reading “Feedback and project schedule performance”

Random rein control

An interesting article in PLOS one explores the consequences of a system of random feedbacks: The Emergence of Environmental Homeostasis in Complex Ecosystems The Earth, with its core-driven magnetic field, convective mantle, mobile lid tectonics, oceans of liquid water, dynamic climate and abundant life is arguably the most complex system in the known universe. This … Continue reading “Random rein control”

Early warnings of catastrophe

There are warning signs when the active structure of a system is changing. But a new paper shows that they may not always be helpful for averting surprise catastrophes. Catastrophic Collapse Can Occur without Early Warning: Examples of Silent Catastrophes in Structured Ecological Models (PLOS ONE – open access) Catastrophic and sudden collapses of ecosystems … Continue reading “Early warnings of catastrophe”

Fun with 1D vector fields

Phase plots are the key to understanding life, the universe and the dynamics of everything. Well, maybe that’s a bit of an overstatement. But they do nicely explain tipping points and bifurcations, which explain a heck of a lot (as I’ll eventually get to). Fortunately, phase plots for simple systems are easy to work with. … Continue reading “Fun with 1D vector fields”

What the heck is a bifurcation?

A while back, Bruce Skarin asked for an explanation of the bifurcations in a nuclear core model. I can’t explain that model well enough to be meaningful, but I thought it might be useful to explain the concept of bifurcations more generally. A bifurcation is a change in the structure of a model that brings … Continue reading “What the heck is a bifurcation?”

A project power law experiment

Taking my own advice, I grabbed a simple project model and did a Monte Carlo experiment to see if project performance had a heavy tailed distribution in response to normal and uniform inputs. The model is the project tipping point model from Taylor, T. and Ford, D.N. Managing Tipping Point Dynamics in Complex Construction Projects … Continue reading “A project power law experiment”

Project Power Laws

An interesting paper finds a heavy-tailed (power law) distribution in IT project performance. IT projects fall in to a similar category. Calculating the risk associated with an IT project using the average cost overrun is like creating building standards using the average size of earthquakes. Both are bound to be inadequate. These dangers have yet … Continue reading “Project Power Laws”