The UK's decision to leave the European Union has rattled the scientific community, amid fears that the so-called "Brexit" referendum could threaten funding for British research and collaboration across the continent.

In a referendum held Thursday, nearly 52 percent of British voters chose to leave the EU, while 48 percent voted to remain. The decision left financial markets reeling on Friday morning, and led Prime Minister David Cameron to announce that he will resign from his position in October. Brexit supporters have argued that the UK should leave the EU to free itself from regulations on its economy and immigration policies, while opponents have maintained that staying in the EU would be better for Britain's economy.

"a disaster for British science"

The British scientific community has overwhelmingly opposed Brexit. A Nature poll of nearly 2,000 scientists living in the UK conducted in March found that 83 percent supported remaining in the EU, while just 12 percent supported leaving the union. Stephen Hawking and around 150 other members of the Royal Society at Cambridge University have said that a vote for Brexit would be a "disaster for UK science and universities."

Much of the concern centers around funding. The EU has budgeted an estimated €120 billion ($134 billion) to directly support research and innovation projects from 2014 to 2020, and Britain has been a major beneficiary. From 2007 to 2013, the UK contributed an estimated €5.4 billion to EU research and development, according to the UK Office of National Statistics. During that time period, it received €8.8 billion in direct EU funding for research, development, and innovation, the Royal Society said in a report published this year.

The Royal Society

The UK is also a major player in international scientific research, accounting for nearly 16 percent of the world's most highly cited articles. Some science associations say that much of its success has to do with its European ties. "Our evidence showed that the UK’s EU membership was regarded as having a mostly positive influence on the effectiveness of UK science, research and innovation, especially with respect to funding and collaboration," Dominic Tildesley, president of the Royal Society of Chemistry, said in a statement Friday.

The impact on the European space industry is less certain. The European Space Agency (ESA) is an inter-governmental organization that is separate from the EU, and the Brexit decision would therefore not affect the UK's membership. But the decision may impact joint EU-ESA initiatives, such as the €4.3 billion Copernicus earth observation program, ESA director general Johann-Dietrich Woerner told reporters last month. Woerner added that a vote for Brexit would have "a negative effect" on the UK space industry.

There are also concerns over restrictions on travel and immigration. More than a third of researchers at Cambridge are overseas nationals, according to the BBC, and 23 percent are from other EU countries. Closing borders and implementing visa requirements could make it more difficult for British universities to attract talent, scientists say, and more difficult for British researchers to participate in cross-border collaborations in Europe.

"Science benefits from the way in which our scientists based here in the UK are able to freely collaborate with scientists in Europe, and there are so many examples of how the scientific community as a whole has benefitted from that interaction," Lord Paul Drayson, the former UK Minister of Science, told Scientific American prior to this week's vote. Drayson pointed to CERN and the Horizon 2020 EU innovation program as initiatives that "have been facilitated through that natural collaboration which comes from being part of the European community."

"The UK does fantastic science, but it does it through collaboration."

Brexit supporters, including the group Scientists for Britain, have argued that UK researchers would still be able to access EU research funds through association agreements, which allow researchers from non-EU countries to compete for European grants in exchange for a lump sum. (Non-EU countries like Norway and Israel currently use association agreements to access EU funds.)

The group has also disputed immigration concerns, arguing that talented scientists and engineers would still be able to qualify for visas, and that the Brexit decision may not necessarily impinge freedom of movement. Others, including Matt Ridley, who sits on the Science and Technology Committee of the House of Lords, have contended that Brexit would allow researchers to engage in more international collaborations outside of Europe.

"If the current terms of non-EU immigration to the UK are taken as a basis, even leaving the EU’s free movement environment is highly unlikely to impede meritorious EU scientists," Scientists for Britain said last year in its submission to a House of Lords Science and Technology Committee inquiry. "In other words, if the UK applied its tightest tests for immigration and movement, the deserving scientists and engineers would in any case meet the Tier 1 or 2 qualification for UK work visas."

"Brexit throws up walls."

But researchers in the UK and abroad remain wary of the future. Katie Mack, an American theoretical astrophysicist at Melbourne University who spent three years doing postdoctoral research at Cambridge University, says her position at Cambridge wasn't strongly dependent upon the UK's membership to the EU. But she believes Brexit will have major implications for her peers.

"The EU offers a lot of the research funding my colleagues currently rely on through various grant programs and fellowships," Mack said in an email. "It will be much harder for universities in the UK to recruit research students and postdoctoral researchers from within the EU, research funding will be less available, and UK researchers' involvement in international experimental and observational collaborations will be at risk."

Jonathan Pritchard, a senior lecturer in astrostatistics at Imperial College London, says it will become more difficult for UK institutions to hire talent within the EU, and he doubts that the UK government will be able to replace the EU grants upon which many researchers depend. "The UK does fantastic science, but it does it through collaboration," Pritchard said in an email. "Brexit throws up walls to that collaboration while doing nothing to support UK science."

"I worked in the US for nine years and came back to the UK, partly because it was home, but also because it was a great base for doing science across Europe," he adds. "This result makes me question that decision."