Why are the Tibetans not invited?

It seems to me that we are still living in the 19th century when the British could negotiate and sign treaties about Tibet without the participation of the Tibetans. 
Remember 1890, 1893, 1906, 1907  and then the infamous Panchsheel Agreement in April 1954. Why are the Tibetans are never invited to discuss their own fate, their own future?
Colonialist China probably think: 'It is not their business!' 
As the 21st Tibetan Task Force for Negotiations is meeting in Dharamsala, it should be the first topic on the agenda: a Tibetan participation to all conferences/study groups/seminars on the ecological future of the Tibetan plateau. 
Are we still living in the 19th century? What is the point to speak about 'autonomy' today, if the Tibetans are not even invited to discuss their future?

Int'l scientists to launch environmental studies on "Third Pole"
Xinhua, March 9, 2010
International scientists are preparing to launch a joint study on the environment of the "Third Pole" region centered on the Qinghai-Tibet Plateau and neighboring areas, a Chinese scientist said Monday.
Like the South and North Poles, environmental changes in the "Third Pole" has attracted increasing worldwide attention against the backdrop of concerns over global climate change, said Yao Tandong, director of the Institute of Qinghai-Tibet Plateau Research with the Chinese Academy of Sciences.
The "Third Pole" region, covering more than 5 million square km at an average altitude of above 4,000 meters, is the birthplace of about 1,000 glaciers in tropical and sub-tropical regions, Yao said.
"The environmental changes in the 'Third Pole' will directly affect the economic and social development in the Qinghai-Tibet Plateau and neighboring countries, and will directly or indirectly affect the livelihoods and even survival of the 1.5 billion residents there," he told Xinhua in an exclusive interview.
Yao, a member of the National Committee of the Chinese People's Political Consultative Conference (CPPCC), made the remarks while attending the ongoing annual session of the country's top political advisory body.
"Due to the global climate change, the 'Third Pole' is experiencing sensitive and marked changes, such as in cryosphere, atmosphere, hydrosphere and biosphere, which are exerting an influence on the social and economic development in the region," he said.
Under the "Third Pole Environment" (TPE) project initiated by Chinese scientists, a group of scientists and science organizations from countries in the region and western countries will gather to carry out joint studies focusing on the competing influences of water, ice, air, ecosystem and human activities in the region, Yao said.
"We hope to reveal the process and mechanism of environmental changes in the 'Third Pole' region, its response mechanism to global climate change, especially the monsoon system, improve the adaptation ability of human-kind for climate change, and help achieve harmonious development between human-kind and nature," he said.
Chinese scientists have conducted studies on the Qinghai-Tibet Plateau for decades, and will further improve their research methods to expand their studies to the "Third Pole" region, Yao said.
During the interview, Yao also offered some negative forecasts for the plateau region due to climate change and human activities.
It is expected that the glaciers in China, located mainly on the Qinghai-Tibet Plateau, would shrink by more than 45 percent in area by 2100, he said.
"In developing glacier tourism, we must protect the environment," he said.
In addition, the area of frozen earth on the plateau would decrease by about 8.8 percent 50 years later and would diminish "drastically" within the next century, he said.
"That will endanger the safety of the highways and railway on the plateau," he warned.
He proposed that the central government continue funding major highway and railway projects to eliminate hidden dangers in roadbeds on top of the frozen earth layer in a bid to ensure the coordinated development of society, economy and the ecosystem in Tibet.