New research suggests large birds and land mammals will face extinction over the next century due to climate change, deforestation, hunting and increased urbanization. The study, published in Nature Communications, says small insect-eating animals that reproduce quickly will fill in the gap.
Species such as rhinos, hippos, eagles and vultures are expected to see the greatest losses, while rodent and songbird populations will grow. The larger animals are known to be less adaptable to changing conditions than their smaller counterparts, making them less likely to survive.
"By far the biggest threat to birds and animals is humankind — with habitats being destroyed due to our impact on our planet," Rob Cooke, lead researcher a postgraduate scholar at the University of Southampton in England, said in a statement.
Larger mammals often play an important role in creating environments for other species so the decline in these species could ultimately be problematic for smaller ones as well. For example, elephants uproot trees, creating open areas and condors scavenge carcasses that might otherwise spread disease to other species. The loss of elephants, condors and other large mammals would remove the benefits they place on the environment and put other animal species in jeopardy.
In order to reach these conclusions, the researchers looked at all 15,484 species of birds and land mammals, considering at five characteristics for each: body mass, diet, breadth of habitat, typical number of offspring and the length of time between generations. They used this information along with data from a list of threatened species to run computer simulations showing various potential extinction patterns.
The simulations showed the average body mass of mammals will likely fall by 25% over the next century, reflecting the loss of bigger birds and animals. Mammals’ average body mass fell just 14% over the past 130,000 years.
These models rely on a lack of changes in human activity, so the outlook for large animals could improve if humans took an aggressive approach to slowing climate change and other factors pushing these animals to extinction.
The researchers say the public can help by putting pressure on policymakers to make changes that will protect these species from excessive hunting, trapping and fishing.