Hunter-gatherers or farmers?
A box full of fresh vegetables arrived at the field station today, courtesy of Georges and his new Puerto Rican community supported agriculture (CSA) group, AGROexpress. Yautilla, starfruit, tomatoes… finding these roots and fruits at my porch was a distinct pleasure. The food I (and probably you) eat is almost entirely grown on a farm, with very little of it gathered in the wild. Looking at this CSA box made me think about the comparison to my science, and where it comes from.
Science lives and dies by data – measurements tell us facts about the real world, and help us build new theory. Without data, science is reduced to speculation or philosophy. But where do these data come from? Are we hunting and gathering it in the wild, or are we actively cultivating it? I think that broadly speaking, ecologists do both. Many times, we simply go out into a new place, and make observational measurements, and take what we can find. Think Darwin and the Beagle, or Lewis and Clark on their expedition across North America. But other times, we set up experiments that help us obtain the data we want. One example of this approach is the the Rothamsted Park Grass experiment, which measures how hay yields respond to long-term fertilization (since 1843!). Another example is the Simberloff-Wilson study of how species colonize islands, achieved by killing all insects on several subtropical islands and measuring the identity and number of species that returned over the following years. With both approaches one obtains valuable data, though through very different approaches.
So what category does our Puerto Rican work fall into? We are a motley mixture of both. We work in a large forest, but it is not an unexplored forest that we simply measure. We are working in a place that has been set up to facilitate learning. Every tree here is given a metal tag that helps identify it over time. As we study the dynamics of the forest, we can rely on these tags. Finding them is our season’s harvest.
Unlike real agriculture, we are always guaranteed a good harvest. Not finding our tags, or finding them on dead plants, is an equally desired result. Above, you see a pile of metal tags we’ve stripped off dead plants; below, you see a palm that died some time between January 2012 and February 2013. However, these deaths help us understand why some individuals succeed and others do not.
We are also hunters. We are keen to understand the functional properties of plants – how much carbon they capture, how much biomass they store – which requires us to collect leaves and stems from many species. For this work, we walk through the forest, grabbing what we can, and bringing it back, tagged, to our field station.
We can turn these materials into numbers through simple measurements in our makeshift laboratory. We don’t know what we will find, and take whatever we can get. Today we were on the lookout for four largeAlchornea latifolia trees, and were only able to find one. Tomorrow we will resume the hunt.
In another week, we will catch a flight from San Juan back to our homes, data stored in notebooks and on hard drives, plant samples safely packed in plastic bags. We will hope to have accomplished enough, to have obtained the data we are seeking. With any luck things will turn out as well as my CSA box did. But it doesn’t really matter how we get these data. We can gather it in wild places or cultivate it in prepared sites. So long as we have it, we will satisfy our hunger for knowledge.