Scientific progress is often portrayed as a march through time. This analogy is a helpful one, except for one key point. Marches are linear. With marches, as we answer questions, we move forward to answer new questions. The size of the frontier of ignorance is invariant.
More than a march, scientific progress is a centrifugal force. For every question we answer, multiple questions are generated. The size of the frontier of ignorance is ever expanding. This isn't just Einstein's "The more I learn, the more I realize I don't know". It's more like, "the more I learn, the more I need to learn."
For ecology, the centrifugal forces are even more acute. There aren't that many more ecologists than there were a few decades ago, but the number of questions that have been generated by the past 30 years of research, not to mention the ever increasing centrality of ecology to societal well-being, dilutes our power to answer questions. That said, it takes a long time to answer any one ecological question. And ecological knowledge is not necessarily globally applicable. Ecological questions have to be tested multiple times for generality.
The number of questions ecology has had to incorporate into its discipline is immense. If the number of ecologists stays constant, the speed at which we answer questions also stays constant, but the number of questions that we are asked to answer increases, which questions are left behind?
The answer is not the less relevant ones, but probably the recalcitrant fundamental ones. Case in point, Grime's Plant Strategies and Vegetation texts (1979 or 2001) has few peers in the literature. The degree of integration among topics and depth of scholarship is admirable. Yet, outside of the CSR triangle, few of the ideas in the book seem to have been recognized in the literature. And the number of independent researchers that have tested CSR probably can be counted on one hand. Tilman's R* theories suffer a similar fate. R* has never been tested in terrestrial ecosystems outside the state of Minnesota.
These are two of the most important theories in plant ecology. The number of citations they have generated are rarely equalled, but they haven't given rise to research proportional to their importance. And it's not because Grime or Tilman answered their questions so completely. So many of the questions that were generated in the early 1980's still lay as unanswered now as then.
There are two reactions to centrifugal forces. The first is to ride the force and keep asking questions at the frontiers. The second is to resist the force to maintain position. Many of the recent developments in ecology are incredibly exciting and deserve a central place within the discipline: urban ecology, invasion biology, conservation ecology, ecogenomics, and climate change research for example. But as we expand to fill these areas, we have to look back and ask how well we have answered the questions we are leaving behind, and whether our ability to answer questions on the frontier will be hindered by leaving the questions that make up the core of our discipline. If we do not work to increase the number of ecologists, or the speed at which we answer questions, than hard choices will continue to have to be made on which questions go unanswered.