Trade, power and climate change

From the Middle Ages, London was the centre of much trade and increasingly a powerful influence on international politics.
These factors had impacts on her nature, through generating need for timber (ship-building), increased importation of timber (which meant we could exhaust our local woodlands) as well as species for ornamentation, or those that inadvertently accompanied ships back to port.
Horse chestnut and sycamore had arrived by the 16th century, as had the black rat, which soon made its home in London's dockyards and houses.
In 1666 the Great Fire of London was followed by the yellow flowering of London rocket in the burnt ashes, a Mediterranean species suited to the laval slopes of Mount Etna.
The Fire also stimulated a new approach to city planning and a move towards brick building.
The Scientific Revolution from the late 16th century led to a growing interest in the natural world; publications of herbals (such as by John Gerard, and William Turner), the first city flora Flora Londinensis (William Curtis, 1779) and growth of microscopy to explore previously invisible worlds (for example, The Aurelian, Moses Harris, 1799).
Britain entered a 'Little Ice Age' between 1600 and the 1790s (with 1664 reputedly the coldest winter in history), during which the Thames froze completely over at least 20 winters (for two months in 1684, and 1715), and became a popular place for Frost Fairs.
However, these conditions imposed greatly on the weak and poor of London, causing crop failures, famine, and early death.
Cold winters would have devastated populations of small birds and mammals, and would have placed increased pressure on woodlands for firewood.
In November 1703 the Great Storm hit London, the most severe hurricane ever recorded in southern Britain; 193 kph winds ripped across the city, lifting the roof of Westminster Cathedral and flinging together 700 ships in the Pool of London.
No records remain of the trees blown down, but they probably numbered millions. 
Plants for parks, gardens, and arboretums began being imported from the 17th century, as well as exotic fauna to astound and amaze, before eventually inhabiting new zoological gardens (at Vauxhall and Regent’s Park).
It was also a period of experimentation; plant selection and animal breeding providing new varieties for agriculture and ornamentation.
A long-lasting legacy from these times is the London plane, a hybrid of occidental plane and oriental plane that probably occurred in Spain.
It first appeared in Britain around 1680 and was planted as an ornamental tree, soon becoming fashionable once it was realised just how tolerant it was to a polluted city life.
Some of London’s oldest examples, from the 1770s, still stand in Richmond, Kew, and Barnes.
In the mid-19th century the fascination with foreign nature was epitomised by the Acclimatisation Society, launched at the feast of an eland (large African antelope) in London in 1859.
The Society sought to brighten up Britain's landscapes with colourful species from around the world, from catfish to wallabies.
Whilst most of these attempts were unsuccessful, we are left with a legacy of these ideas which have never entirely vanished - for example, rhododendron, Japanese knotweed, Mandarin duck, little owl, grey squirrel, and muntjac deer.
These joined species that hadn't specifically been invited, such as brown rat, and cockroaches.