Research Spotlight: Why our longleaf pine habitats in the southeast are not forests but savannas and why it matters

If you find yourself in a longleaf pine savanna, remember to look down. Although this habitat is named for the dominant tree species, most of the biodiversity is in the understory. In one square meter on the ground – which is probably smaller than the hood of your car – there can be more than 50 different plant species. Many of these species occur nowhere else on Earth and support endangered animals such as gopher tortoises and other critters that may be hard to spot. If you do look up, you’ll see not just the green canopy of the longleaf pines, but also plenty of blue sky. That’s because a combination of frequent fires and other factors keep the mature longleaf trees relatively far apart. Longleaf canopies let plenty of sunlight reach the understory, one key reason why it is so biodiverse. A forest, on the other hand, has a closed canopy casting deep shade underneath. Though the longleaf habitat is very much a savanna, it is often mistakenly called a forest. This distinction matters for how we manage longleaf as a healthy ecosystem.

Not long ago longleaf pine savannas blanketed the Coastal Plains along the Gulf Coast. This habitat was the dominant land cover, stretching its reach from eastern Texas to southern Virginia and about halfway down the Florida Peninsula. Logging in the 1920’s drastically altered the landscape and reduced the range of longleaf habitat. Today it is estimated that only 3% of the historic range of longleaf remains.

One focus of management today is maintaining frequent fires, burning about every 1-3 years. Because these high frequency though low intensity fires are natural in our lightening-prone region, it is actually fire suppression that is the problem. Remaining longleaf habitat exists in a patchwork of different land-uses and sprawling development, which hinder fire. And you can imagine that frequent prescribed fires aren’t popular where lots of people live. Another issue is increasingly stronger and stronger hurricanes, which are becoming more common along the Gulf and Atlantic Coasts. These unprecedented storms are wiping out remaining longleaf habitat in such a destructive way that traditional restoration strategies may not work any longer[1].

Those with boots-on-the-ground in the region understand these challenges. However, a global issue that is creeping into the conversation is climate change. An admittedly logical solution to climate change is to plant more trees which store carbon naturally. Thus there have been high profile academic publications that map regions on Earth as “understocked” forests in an attempt to identify places where we should be planting more trees[2],[3]. Unfortunately, many of the regions that some distant academics think should be planted with more trees are longleaf savannas as well as other savanna regions around the world.

Tree planting campaigns are ubiquitous these days, even outside of academic publications. Just today I listened to an ad for a credit card company that promised to plant a tree with every swipe. But the solution to climate change is not as easy as swiping your credit card, which might do more harm than good. For one, it is unclear if planting more trees in savanna regions will sustain itself as a “forest” as these regions have been savanna for millions of years[4]. A forest is more than just the trees. An ecosystem is built on interdependent relationships between species – from microbes to insects to birds – and their specific environment such as the soil, climate, and hydrology. So just planting trees does not mean a functioning forest will appear. If we plant more trees in longleaf habitats and other savannas around the world we will lose the high-light conditions in the understory and exceptional biodiversity that these regions support. We need to think twice before planting trees everywhere. A better and more cost-effective solution to climate change is protecting our remaining intact forests and savannas, and preventing ecosystem destruction in the first place.  

[1] Zampieri, N. E., S. Pau, and D. K. Okamoto. 2020. The impact of Hurricane Michael on longleaf pine habitats in Florida. Scientific Reports:1–11.

[2] Domke, G. M., S. N. Oswalt, B. F. Walters, and R. S. Morin. 2020. Tree planting has the potential to increase carbon sequestration capacity of forests in the United States. Proceedings of the National Academy of Sciences U.S.A. 117:24649–24651.

[3] Bastin, J., Finegold, Y., Garcia, C., Mollicone, D., Rezende, M., Routh, D., Zohner, C., and T. W. Crowther. 2019. The global tree restoration potential. Science 79:76–79.

[4] Fleischman, F., S. Basant, A. Chhatre, E. A. Coleman, H. W. Fischer, D. Gupta, B. Guneralp, P. Kashwan, D. Khatri, R. Muscarella, J. S. Powers, V. Ramprasad, P. Rana, C. Rodriguez Solorzano, and J. W. Veldman. 2020. Pitfalls of tree planting show why we need people-centered natural climate solutions. BioScience 70:947–950.

Dr. Stephanie Pau is an assistant professor in the Department of Geography. She studies biogeography, biodiversity conservation, climate change and remote sensing.

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