What is a 'Green Structure'

I was talking to a student yesterday who asked me to define a 'Green Structure'. Here's how I responded:

A quite broad definition, includes all the green space, even water of all kinds: lakes, ponds, rivers, stream and coastlines, which is to be found within a city. Green spaces outside the city or urban areas are not a part of a 'Green Structure', but are of course of great importance for urban nature as well as for the city's inhabitants and climate. The focus when discussing 'Green Structure'is the green structure in the city and its most important connections with the surroundings.

In my opinion, all city nature is more or less cultivated. That is why I'd use a broad definition to explain categories which include natural remnants as well as built up areas of several types. The following categories are parts of the green structure: all kinds of water as mentioned above, ‘natural spaces’, pedestrian areas, parks, areas for sports, churchyards, areas surrounding public and private institutions, playing grounds of different types, allotment gardens (we have few if any of these in Ireland) and private gardens. Natural areas are often green spaces along rivers and streams and corridors for walking or left-over areas where people live, along roads and so on. Remnant nature might also be found in pedestrian areas, parks and churches/graveyards.

The green structure has many functions and values within a city: as a part of the communication system for walking and cycling, recreational functions, as important elements of the landscape, elements connected with history, habitats for plants and animals etc.