8. Why didn’t Portugal follow up on Mendonça’s visit to Australia and New Zealand?

Preamble: The Treaty of Tordesillas, signed in 1494, was an agreement between Spain and Portugal to divide newly discovered lands outside of Europe. It established a line of demarcation, with Spain claiming lands to the west and Portugal to the east. This division aimed to prevent conflict between the two powers during their age of exploration and colonisation.

The Portuguese had strong incentives to keep any discoveries secret, given their intense rivalry with the Spanish and the territorial divisions imposed by treaties like Tordesillas and Zaragoza. Up until 1529, they may have feared how their findings would be interpreted under the Treaty of Tordesillas 1494. Once the Treaty of Zaragoza was negotiated in 1529, placing eastern Australia and New Zealand in Spain’s sphere, the Portuguese likely remained silent to avoid alerting their major competitors.

Portugal did not pursue further exploration of Australia and New Zealand after Mendonça’s voyage due to the Treaty of Zaragoza alongwith more pressing priorities in the following decades. The search for the Isles of Gold had yielded no success, and instead, Portugal focused on establishing colonies in Angola, Brazil, and Macau, as well as expanding its trade networks in India, Sri Lanka, and the Maluku (Spice) Islands. Since Mendonça had not identified wealth-generating opportunities in Australia or New Zealand, they were not seen as valuable additions to Portugal’s growing empire.

The Portuguese defeat in North Maluku in 1575 weakened their influence in Southeast Asia, allowing the Dutch to take over many of their trading posts. Portugal's presence was reduced to territories like Solor, Flores, Timor, and the Nusa Tenggara region, ending entirely with the Indonesian invasion of East Timor in 1975.

Had Australia or New Zealand offered compelling economic opportunities, Portugal’s trajectory in the region might have been very different. But at the time, their ambitions lay elsewhere, in regions where wealth and trade were more tangible.

One major reason the Portuguese kept Mendonça’s discovery secret was to prevent other European powers from reaching the new land. Additionally, the Great Earthquake of 1755 destroyed Lisbon and the Casa da India, which held all maritime records. Fortunately, French spies managed to obtain Mendonça’s map of the east coast of Australia and the North Island New Zealand, either shortly after it was deposited in the Casa or through French pirates who raided returning Portuguese ships.