For many people, eating chocolate is their go to response to anxiety attacks. Hey, it's less damaging than alcohol. There's an irony, however, because the more soothing the chocolate, the more stressed the trees from which it came.

There are plenty of ethical concerns when it comes to eating chocolate. If you're not careful what you buy, it's likely child slaves harvested the cacao beans that went into your bar, or endangered species died to make room for the plantation. Fortunately, however, fair trade and rainforest certified brands are available for those who care about such things.

Yet even ethical consumers probably don't think about whether the cocoa trees that give us their glorious fruit are themselves stressed. Fortunately, it's scientists' job to send their minds places others don't go, and University of Goettingen PhD student Wiebke Niether is one who has been investigating what makes for good cocoa, and the effect of environmental stress on the trees.

Niether compared trees grown in mixed-species plantations with those in monocultures where cocoa plants are surrounded by their kin, which compete with them for the same nutrients. Mixing cocoa trees in with taller plants that shade them, and extract different nutrients from the ground, has been thought to benefit them. In the Journal of Agricultural and Food Chemistry, Niether and her co-authors compare beans from five cocoa plantations with samples harvested at different stages of the growing season.

To their surprise, the type of plantation produced barely detectable differences in the beans, although the antioxidants that give chocolate its complex flavor were slightly more concentrated in beans grown in monocultures. Antioxidants such as phenols not only account for chocolate's distinctive flavor, they are also the reason why it appears that (low-sugar) dark chocolate can be healthy.

On the other hand, weather conditions proved much more significant. In the course of the dry season, soil moisture fell since cocoa plantations are seldom irrigated. This increased the beans' antioxidant levels, a common plant response to stress, and decreased fat composition.

Changing rainfall patterns as a result of global warming will mean some cocoa-growing areas may become wetter, but the more common trend is likely to be towards longer and hotter dry seasons. Chocolate manufacturers are concerned this will reduce production. Niether's findings suggest that while the quantity is likely to decline, we might get some compensation in exceptionally high-quality chocolate. Sadly, this outstanding chocolate may be so scarce only the very rich will be able to afford it, a thought that should stress more than the trees.