Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How large is the Boreal Shield in km2?

### Inputs:
table_name: table, columns: ['Ecozone', 'Area (km²)', 'Percentage of total area', 'Percentage of land area', 'Percentage protected']

### Response:
SELECT COUNT Area (km²) FROM table WHERE Ecozone = Boreal Shield