253
Figure 173.
Percent extinction occurrences as reflected in the fossil record have fluctuated
throughout Earth’s history. Sudden and dramatic losses of biodiversity, called
mass extinctions
,
have occurred five times
139
.
Reading #3: Threats to Biodiversity
The combination of population growth and resource exploitation is the primary threat to the
planet's
biodiversity and, consequently, to human welfare. Resources
are being removed from the
environment in an unsustainable manner while the human population needs them to live and thrive.
The three main immediate threats to biodiversity are invasive species, habitat loss, and overfishing.
The first two of these are a direct outcome of resource use and population growth. The third results
from increased mobility and trade.
Anthropogenic climate change,
the fourth major cause of
extinction, has not yet had a significant effect but is expected to do so this century. The need for
energy by the human population and the use of fossil fuels to meet those needs are additional causes
of global climate change (Figure 174). Environmental issues, such as toxic pollution, have specific
targeted
effects on species, but they are not generally seen as threats at the magnitude of the others.
139
Clark M.,Choi, J. Douglas M. (2020)
Biology 2e
. Chapter 47, -Pp.1377-1378. OpenStax,
https://openstax.org/details/books/biology-2e
)
