Humans will eventually succeed in utilizing all Earth’s land mass area for their own purposes. We are already almost 80% there. Our future success depends on the continuing prosperity of most of the native plants and animals in this wonderful new world. This is a great problem that confronts us.
There are about 130 million km^2 of ice-free land on Earth. Before humans took over, these were classified by vegetation type into distinct biomes, noting areas of human disturbance. Now that we are ubiquitous across most of this area, it makes more sense to classify the land by sustained human land use.
We now consider Earth’s land area as comprised of 18 types of anthrome (anthropogenic biome). We are imbedded in our anthromes, our status being elevated from disturbers to permanent managers. Anthromes comprise 101 million km^2. The remaining 29 million km^2 is still virgin land, principally in Siberia, northern Canada, the great desertsof Africa and Asia, and much of the Amazon basin. Examples of anthromes are Populated Forest (12 million km^2), Irrigated Cropland (2.6 million km^2), and Urban (1.3 million km^2).
Our anthromes fragment native biomes. There is a fundamental species-area relationship formula (SAR), derived from study of many data sets of counts of species (S) in a known area (A): S = cA^z, where c corresponds to the number of endemic species in 1 unit of Area, and z varies with several characteristics of the data set, but usually ranges from .15 for contiguous land area, to .3 for disconnected areas and islands. The more the contiguous area, the much more the species.
A typical forest fragmentation resembles a fishbone pattern, where a road is cut for access to the interior area, then other roads intersecting the original, where plots accessible from the roads are then cleared and repurposed for timber harvest and subsequent agricultural and stock grazing uses. After fragmentation occurs, the count of species on the remaining land rises briefly (the refugee effect), then falls indefinitely with no new equilibrium achievable, as the native biome gets repeatedly sliced and diced.
To have the land under our management be able to support the largest possible number of endemic species, individual plots purposed as natural areas should be connected in such a way that a contiguous range of largest possible area is made accessible to local species.
Managing of anthromes is a global issue. Each country must manage its own, but cooperative research, planning, and development is to be wished. The USA has been increasingly conservationist through the 20th century. In our urban areas, enlightened planned developments have implemented contiguous green belts that are left in a natural state. Land conservancy groups continue to rescue open land from private ownership, to create contiguous blocks set aside for re-wilding. We have been protecting our wetlands for a number of decades, although sadly not in time to save most of their original area.
Further on the side of nature, many animal species are proving adaptable to living in our anthromes, including birds and mammals smaller than the wolf. It is the larger mammals that the world must manage more carefully, the apex land predators: wolf, bear, lions and other large cats. Many large herbivores also are currently threatened, such as the bison in North America, and the rhino, hippo, and elephant in Africa and SE Asia.