American Scientist

To the Editors:

It is truly remarkable how ancient Egypt provides so much insight into our modern ecological landscape (“Modern Lessons from Ancient Food Webs,” May–June). As a student inside the Biosphere 2 Center in 1998, I witnessed firsthand how the loss of biodiversity plagued the stability of a closed system. Nearly two decades later, we are seeing our oceans, rainforests, and marshes face unprecedented challenges as human pollution, climate change, and a lack of good stewardship practices threaten real-world food webs across our planet. We have a responsibility as leaders, to learn from the past, both ancient and recent. Biodiversity and the preservation of species in the wild not only impact the balance of food webs but are also vital to our health, wellness, and economic stability. Perhaps most overlooked is the fact that biodiversity is more than just a scientific concept—it is fundamental to the richness of the human experience.

Michael Aaron Gallagher
Syracuse, NY

To the Editors:

The article “Modern Lessons from Ancient Food Webs” by J. D. Yeakel and J. A. Dunne describes the building of measurable mathematical models, such as discrete food webs, that can describe the various relationships and states that exist in the biomass of different ecosystems. However, in their discussion, to say that the food web models of the post–African Humid Era in the Nile Valley show that its ecosystem has collapsed (or is collapsing) seems biased against its obvious human success. Are not human populations and all their associated domestic agricultural biomass as legitimate a part of any food web as the nondomesticated ones? Would it not be more accurate to describe the current ecosystem of the Nile Valley area as containing an essentially successful system, albeit one that has changed greatly in the past 6,000 years? This new food web, were it not dominated by contriving humans and their associated plants and animals, might be described as similarly successful as the new food web systems that originated during the mammalian revolution of the Eocene.

If the current dominant human-associated biomass of the Nile were fully included in any comprehensive food web model, wouldn’t a nonhuman observer describe it as a success rather than a collapse? Considering the staggering climatic changes that have occurred since just before the establishment of ancient Egypt’s first dynasty, some might say that life along the Nile has done quite well.

Richard V. Ascoli
San Luis Obispo, CA

Drs. Yeakel and Dunne respond:

Mr. Ascoli is correct to point out that there are many different ways to evaluate the functioning of an ecosystem, and the alterations that humans have introduced cannot be ignored. In many systems, anthropogenically influenced biodiversity (including species that we directly control, such as food crops) dominates in terms of biomass over what we might consider “natural” or “nonanthropogenically influenced” biodiversity. In these systems, although the biomass of human-controlled species might outweigh others, the vast majority of biodiversity in terms of species richness is facilitated by systems that have not historically undergone significant alteration by humans.

Our analysis of the mammalian community across Egyptian history was intended to assess the functioning of a biological community that had existed before human populations significantly altered species distributions and abundances. Understanding how natural systems change over time—in response to both natural and human-influenced disturbances—will help us understand how ecosystems may be expected to change in the future. Because no “natural” or “human-influenced” ecosystem is entirely separate (indeed, they have very significant impacts on each other), understanding how either might respond to different types of disturbances is vital for maintaining and conserving future sources of biodiversity.