Climate change and the sixth mass extinction

Polar bears (<em>Ursus maritimus</em>) are the poster child for the impacts of climate change on species, and justifiably so.
Polar bears (Ursus maritimus) are the poster child for the impacts of climate change on species, and justifiably so. To date, global warming has been most pronounced in the Arctic, and this trend is projected to continue.

Our planet is in crisis. Due to the actions of humankind, we may be in the midst of a sixth mass extinction. Through habitat destruction, overexploitation, introduction of invasive species, pollution, and most recently climate change, we have set our world on a course from which it may not be able to recover.

Climate change is one of the greatest threats that we face and it’s already having a significant impact on species around the globe. From the shrinking Arctic habitat of ice-dependent polar bears to increasing water scarcity driving wildlife declines in Africa, these changes will become more and more severe in the years to come.

Species are affected in varied and complex ways, and we are only beginning to understand these impacts, many of which tend to occur over longer time periods and require historical data to make a comparison. We’ve already discovered some stark changes however:

  • Some species are on the move. Butterflies, for example, are shifting their home ranges toward the poles and higher elevations. Climate is the most important predictor of butterfly species distribution, and recent change has made their historic ranges less suitable.
  • Life cycles are shifting and causing complications. Responding to warmer spring temperatures, plants are flowering earlier than they used to, resulting in a mismatch between peak plant growth and the animals that depend on them. These changes in the timing of life cycle events often have serious consequences for species that depend on other species for their food source, like an insect and its host plant.
  • Driven largely by warming ocean temperatures, we are in the midst of the longest ever-recorded global coral bleaching event, and it is affecting more reefs than ever before. When corals bleach, they expel the algae (zooxanthellae) living in their tissues and turn white, often leading to the coral’s death.
  • Parts of southern Africa are experiencing the worst drought in over a century. The situation for wildlife is so dire that in some areas park authorities are forced to seek alternate refuge for animals or even consider culling them.
  • As winters get warmer and shorter, insect pests are surviving in ever increasing numbers and affecting other species. Moose populations in North America, for example, are declining due to winter ticks. A single moose can house as many as 150,000 ticks, and are prone to anemia, exhaustion and eventually death.
  • Amphibian populations are declining worldwide, and in some cases species are even going extinct. This is being driven in part by chytrid fungal infections which are thought to be on the rise due to increasing temperature variability. Nicknamed Toughie, the last known Rabbs’ fringe-limbed tree frog in the world recently died in captivity, sending its species the way of the dodo.

However, few of these impacts are driven solely by climate change. Rather, climate change is a threat multiplier, exacerbating existing threats to species. WWF is working to better understand how species are being impacted in a changing climate, and altering our conservation strategies to address this. Additionally, an emerging area of focus in this field, being led by WWF and others, is researching how rural communities around the world are responding to changes in weather and climate, and how their responses may be impacting biodiversity. These “human responses to climate change” have been overlooked in most research to date.

If our planet warms by 2-3°C, it will be difficult to maintain many ecological systems. It’s critical to curb our greenhouse gas emissions to limit the worst impacts of climate change, while realizing that we are already committed to some amount of warming that we can’t stop. The Paris Agreement is a big step in the right direction, but we cannot stop there. We need to take bold, proactive actions that help species adapt, both through direct human interventions and by facilitating their natural capacity to adapt to these changes.

This post is part of a series on the Living Planet Report, WWF’s biennial science-based analysis on the health of our planet and the impact of human activity. To read all the posts in this series click here.

Gorillas don’t drink much water, so how might they be vulnerable to water scarcity? Community members living nearby will encr
Gorillas don’t drink much water, so how might they be vulnerable to water scarcity? Community members living nearby will encroach on the national parks during increasingly frequent dry periods. While collecting water, they often set snares. Though targeted at antelopes, baby mountain gorillas get caught as well.
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