
Pollution can be local or widespread.
Substances dumped into a river will often
end up in the sea. The biggest pollution
problem is global warming. This happens when
greenhouse gases, such as CO2
are released into the atmosphere, trapping
heat and causing the planet to warm up.
Since species are adapted to particular
climates, when the Earth warms up they have
to move to keep comfortable. This can be
difficult if natural habitats are isolated
by human settlements and agriculture.

Chemical pollutants have been responsible
for affecting the reproductive organs of
fish, alligators and polar bears, preventing
them from producing babies. Chemical
pollution in the environment also affects
humans - 46 US states have issued warnings
against eating local fish because of dioxin
contamination, and in Europe, human breast
milk passes on more dioxin to our babies
than is legally allowed for cow's milk.
Despite this, the amount of pesticide
sprayed on our crops around the world has
increased 26 times in the last 50 years.
