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30.04.2021 22:59:30
Everyday Connection: Preventing Habitat Destruction with Wise Wood Choices
See full version: 47. 3: Threats to Biodiversity
Everyday Connection: Preventing Habitat Destruction with Wise Wood Choices
Figure \(\PageIndex<1>\): Atmospheric carbon dioxide levels fluctuate in a cyclical manner. However, the burning of fossil fuels in recent history has caused a dramatic increase in the levels of carbon dioxide in the Earth’s atmosphere, which have now reached levels never before seen in human history. Scientists predict that the addition of this “greenhouse gas” to the atmosphere is resulting in climate change that will significantly impact biodiversity in the coming century.
Figure \(\PageIndex<3>\): The brown tree snake, Boiga irregularis, is an exotic species that has caused numerous extinctions on the island of Guam since its accidental introduction in 1950. (credit: NPS) here
Lakes and islands are particularly vulnerable to extinction threats from introduced species. In Lake Victoria, the intentional introduction of the Nile perch was largely responsible for the extinction of about 200 species of cichlids. The accidental introduction of the brown tree snake via aircraft (Figure 4) from the Solomon Islands to Guam in 1950 has led to the extinction of three species of birds and three to five species of reptiles endemic to the island. Several other species are still threatened. The brown tree snake is adept at exploiting human transportation as a means to migrate; one was even found on an aircraft arriving in Corpus Christi, Texas. Constant vigilance on the part of airport, military, and commercial aircraft personnel is required to prevent the snake from moving from Guam to other islands in the Pacific, especially Hawaii. Islands do not make up a large area of land on the globe, but they do contain a disproportionate number of endemic species because of their isolation from mainland ancestors. here
The shifting ranges will impose new competitive regimes on species as they find themselves in contact with other species not present in their historic range. One such unexpected species contact is between polar bears and grizzly bears. Previously, these two species had separate ranges. Now, their ranges are overlapping and there are documented cases of these two species mating and producing viable offspring. Changing climates also throw off the delicate timing adaptations that species have to seasonal food resources and breeding times. Scientists have already documented many contemporary mismatches to shifts in resource availability and timing. [links]
Figure 7. The effect of global warming can be seen in the continuing retreat of Grinnell Glacier. The mean annual temperature in Glacier National Park has increased 1.33°C since 1900. The loss of a glacier results in the loss of summer meltwaters, sharply reducing seasonal water supplies and severely affecting local ecosystems. (credit: USGS, GNP Archives) [links]
Link to Learning: Explore this interactive global database of exotic or invasive species. here
Overharvesting is a serious threat to many species, but particularly to aquatic species. There are many examples of regulated fisheries (including hunting of marine mammals and harvesting of crustaceans and other species) monitored by fisheries scientists that have nevertheless collapsed. The western Atlantic cod fishery is the most spectacular recent collapse. While it was a hugely productive fishery for 400 years, the introduction of modern factory trawlers in the 1980s and the pressure on the fishery led to it becoming unsustainable. The causes of fishery collapse are both economic and political in nature.
Here’s a look at each region’s average decline between 1970 and 2016: more
Today’s graphic uses data from WWF’s Living Planet Report 2020 to illustrate the biggest threats to Earth’s biodiversity, and the impact each threat has had globally.
Latin America & Caribbean has seen the biggest drop in biodiversity at 94%. This region’s drastic decline has been mainly driven by declining reptile, amphibian, and fish populations.
When looking at the regional breakdown, the order of threats in terms of biodiversity impact is relatively consistent across all regions—however, there are a few discrepancies: [links]
Not specifically mentioned in the analysis are corals, which have become a kind of poster child for climate change. Coral reefs have been devastated by the “longest and most widespread“ bleaching event on record, a phenomenon in which stressed corals expel algae and turn white, often as a result of warming ocean temperatures. [links]
“If we don’t address them, we’re going to lose most of our biodiversity, no matter what we do about climate change,” he told the publication.
Addressing “old foes,” Maxwell said in a statement, will be “key to turning around the biodiversity extinction crisis.” here
A new analysis of threatened wildlife has provided a much-needed dose of perspective, showing that age-old human activities, including logging, hunting and farming, continue to pose a greater and more urgent threat.
The group found that over-exploitation, including logging, hunting, fishing and the gathering of plants, tops the list of biodiversity’s “biggest killers,” affecting 72 percent of the 8,688 species listed by IUCN as threatened or near-threatened. Agricultural activity impacts 62 percent of those species, while urban development and pollution threaten 35 and 22 percent, respectively.