2. Habitat modification
There are many ways that habitats can be modified, and again there are direct and indirect threats. The key processes that result in habitat modification for aquatic species, ranked from highest to lowest threat level, are:
In general, coastal species are more exposed to threats from habitat degradation than pelagic or deep-water species because they are simply closer to the activity. In coastal ecosystems, the main threatening processes are residential and commercial development, destruction of critical habitats such as mangroves, changes to rivers (river engineering) and pollution. These 4 processes alone threaten nearly 1/3 of all threatened sharks and rays.
We learned about plastic pollution in lesson 7 however pollution comes in many forms. These include urban waste water, effluents and garbage.
It is estimated that about 6% of elasmobranchs are threatened by pollution. Pollution can make habitats unsuitable for species to live in and many can be toxic for animals exposed to them, or cause harm or death from entanglement.
4. Climate change
We’ve already learnt a lot about Climate Change, again we can apply our learnt knowledge to various species. Remember our oceans play an integral role in regulating greenhouse gasses, however there is a limit to what the oceans can handle.
Warming air temperatures mean warming ocean temperatures. Warming oceans cause ocean acidification which is disastrous for coral reefs and the species which rely on these ecosystems. Warming oceans may also make habitats unsuitable for many species. For some species, shifting their range towards the poles may work. We have seen poleward range shifts in many species already, including Port Jackson sharks (Heterodontus portusjacksii) and smooth stingrays (Bathytoshia brevicaudata) but for others that rely on other habitat requirements, this may be impossible.