Instead of trying to come up with might seem a reasonable assumption about how many animals or plant species there should be in any given area based on modern data or what seems a comfortable number to us, wouldn’t it make a lot more sense to find out what the historic populations used to be—before massive human intervention?
In other words how do we decide today how many deer, wolves, salmon, or birds there should be in our environment before we either take them off or put them on an endangered species list? How many animals or plants and it what proportions make up an healthy environment? We’re just guessing unless we really go out an examine all the data we can to find out what the baseline used to be for particular species in particular places.
One such project is going just that in our oceans: History of Marine Animal Populations "Is a global research initiative. We study the past ocean life and human interaction with the sea. About 100 researchers have joined forces to develop an interdisciplinary research program using historical and environmental archives. We analyze marine population data before and after human impacts on the ocean became significant. Our goal is to enhance knowledge and understanding of how the diversity, distribution and abundance of marine life in the worlds oceans changes over the long term. "