Visionary Science, Ethics, Law and Action in the Public Interest

Trends as Effective Scientific Evidence in Public Policy

Carolyn Raffensperger

Carolyn Raffensperger

Information about trends can be important scientific evidence, according to Amy Kyle, a scientist at Berkeley.  In regulatory debates, the regulated industries want to limit the relevant evidence to studies that “prove” cause and effect.  This means that information, like trends can be excluded. Trends indicate a change in pattern over time.  This week, scientists published a landmark study of trends in Nature magazine.  In the article, Planetary Boundaries, they examine nine system conditions and set parameters that should not be crossed if we expect to maintain a “safe operating space” for humanity. They look at climate change; rate of biodiversity loss (terrestrial and marine); interference with the nitrogen and phosphorus cycles; stratospheric ozone depletion; ocean acidification; global freshwater use; change in land use; chemical pollution; and atmospheric aerosol loading. The scientists that developed this framework understood that ecosystem health isn’t a matter of one statistic or one trend, it’s a multi-dimensional pattern over time.  But as important, they showed that if we wait for proof about cause and effect, it will be too late.  The trends provide enough information to take precautionary action now.

If Kyle is right (which she is), and if the Planetary Boundary system conditions are even in the ballpark (which they are),  the question is how can we use trend data to effectively change public policy? Here are some ideas.

1) Create Early Warning Mechanisms and Institutions. Trend data can serve as warnings that things are amiss. Work on the precautionary principle made clear that many environmental actions were taken too late because we hadn’t acted on early warnings. In fact, one of the lynchpin reports in Europe was called Late Lessons from Early Warnings.  This report documented the history of numerous chemicals where we had lots of information but failed to act until too late in the game. Asbestos, lead, DES, are all prime examples from the report of action taken after enormous harm had already taken place.

We have a few models of government institutions that track emerging trends and respond to prevent further harm. Public health surveillance of hospital admissions is used to identify, track and stop food-borne illnesses. We also have a governmental pharmaceutical adverse response alert system: doctors are required to notify an agency about adverse responses to vaccines. But there is very little in place to respond to longer-term, chronic problems and there are very few systems in place to respond to nonhuman environmental trends. So we need to create more reporting systems and early response mechanisms that can respond to trend information about environmental problems in advance of absolute proof of causation. Imagine hot-lines and swat teams located at public health or environmental agencies that can act on early warnings and trends of loss of pollinators or birth defects.

2) Set Goals and Measure Progress. Once we have base-line information about, say, the increase in learning disabilities among grade school children or the decline of raptors, we can set goals and use trend lines to measure our progress in meeting those goals. The U.S. Dept of Health and Human Services sets goals by decade for public health.  This is a great start and can serve as a model for other areas of environmental policy such as ocean and forest health.

3) Empower Scientists as Detectives. Trend data can be used by scientists trained to think like detectives. Tracking clues, using multiple disciplines, solving mysteries expand the sometimes narrow, reductionist science used in public policy. We already have some models for this in public health departments that must track down and stop food-borne illnesses or intervene in deadly epidemics. We need to apply these same skills to the longer-term, chronic problems and go beyond the human population.

4) Increase Use of Layperson Science. Systematic and regular data collection by lay experts provides remarkably good trend information. For instance, annual butterfly and bird counts done by lay experts across the country provide dependable, accurate trend data on various species. Declines in species are indicators of ecosystem health (or lack thereof) and can be used to require such changes as decreased pesticide use, increased native plantings in public spaces like roadways and evaluations of the implications of climate change. Citizen science can also be used to generate sophisticated hypotheses about cause and effect.

5) Aggregate Trends of Trends. Aggregated trends provide a bigger, more accurate picture of the world because they offer a systems perspective rather than a snapshot of a single parameter. There are two wonderful examples of this available online. One example is the trend analyzer created by the Global Footprint Network. The other is the nine parameters put forward in the article on Planetary Boundaries in Nature magazine described above.  When we assess the larger patterns laid out by trends of trends we have a far better sense of the precautionary actions we must take.

One other thought on trends. Trends are to time what clusters are to space. Trends are patterns in time. Clusters (say of cancer or marine dead zones) are patterns in space. Our survival as a species depends on accurate pattern recognition of both trends and clusters.

Trends help increase the signal to noise ratio. Trends don’t usually provide information about causes but they do tell us if we are heading in the right direction.


  1. Juliet says:

    This is so simple and profound. I love the truth that “ecosystem health isn’t a matter of one statistic or one trend, it’s a multi-dimensional pattern over time.”

    The concept of establishing baseline information, setting goals and then using trend lines to measure our progress toward those goals is so simple it seems like we should already be doing it. It’s kind of troubling that largely we aren’t. I don’t think our existing institutions are set up to track or think this way. I wonder what existing entity or group of entities could be adapted to do this and/or what new entity could be set up to? The EPA total maximum daily load (TMDL) program for water quality is somewhat in this ilk. Maybe if baselines and goals were established and data made available in a central location, the trend tracking could be “crowdsourced”?

    I dig the idea of empowering scientists to think like cross-discipline detectives and tapping into the resource of the lay person and their observation and tracking within their own spheres.

    This is wonderful. Thank you Carolyn!