While thoughts of the tropics provoke pictures of lush green rainforests bursting with colour and unearthly sounds, this is only a part of the story and there are significant tracts of overlooked habitat urgently needing help, according to new research*. Dry forests and savanna account for more than half of the tropics, yet scientists, conservationists and governments have consistently ignored them, not realising these "forgotten forests" hold answers for the future in the climate emergency.

With a wealth of expertise in the botany of dry forests, the Royal Botanic Garden Edinburgh (RBGE) has completed a 10-year research programme resulting in the publication of a new protocol for measuring the health of measured out plots in these forests. This is the first step in identifying and repairing damage, with implications for local to global land use and conservation.

Dr Peter Moonlight, a Tropical Biodiversity Scientist at RBGE, explained that while undertaking exploratory fieldwork to find new plant species in the dry forests of Brazil and Peru, there was a wider commitment to understanding of the health of tropical habitats. Until recent years, the emphasis has been on rainforests, leaving dry forests under investigated. Using the same techniques for both kinds of habitat will go a long way to providing a clearer steer for conservation and land management.

He explained: “One of the most important methods we have at our disposal to understand the health of forests is to build and monitor permanent plots. In these half-hectare sections every single tree is tagged, measured and identified. This sounds simple but is a slow and often difficult process. Tropical forests are not easy places to work, dense – often spiny and  full of biting insects - it can take a team of four people upwards of a week to measure a single plot. However, it is absolutely worth the effort.”

By monitoring these plots over a period of years, it is possible to see connections in the ratio between trees dying and others being established, obtain data on how species composition of the forest could be changing and gather information on whether forests are releasing or capturing carbon. The resulting data can provide crucial insight for a spectrum of decision-making issues, from local conservation planning to building global models of carbon dynamics.

The lack of study in dry forests has partly been because it is much more complicated than in a rain forest. The trees in dry forests are usually much smaller, often spinier, and have many more branches at ground level, meaning they are much more difficult to measure.

“To have more or less ignored the health of dry forests in pursuit of data on rainforests has been a huge omission,” added Peter Moonlight. “As the world's tropics are predicted to become hotter and drier as climate change progresses, we need to understand how those ecosystems already adapted hot and dry environment will react to the changes.”

The RBGE-led protocol for permanent forest plots in dry forests is published today in the journal Plants People Planet https://nph.onlinelibrary.wiley.com/doi/full/10.1002/ppp3.10112 and funded by the Natural Environment Research Council (NERC). *Expanding tropical forest monitoring into Dry Forests: the DRYFLOR protocol for permanent plots is the result of over a decade of field experience in Latin American dry forests and a new collaboration between the DryFlor, RAINFOR, and NordEste networks.

With this new protocol, the ambition is that many of the next generation of permanent forest plots will be established in tropical dry forests and they will no longer be the forgotten forests.