J. Scott Applewhite/AP

Ambassador William Taylor, is escorted by U.S. Capitol Police as he arrives to testify before House committees as part of the Democrats' impeachment investigation of President Donald Trump, at the Capitol in Washington, Tuesday, Oct. 22, 2019.

Editor’s note: This article was updated at 5:45 p.m. on Oct. 22 to include testimony from senior U.S. diplomat William Taylor Jr.

A key part of the House impeachment inquiry into President Donald Trump involves three Latin words: quid pro quo, literally “this for that.” Did President Trump withhold aid from Ukraine to pressure it to launch an investigation that might benefit him politically?

Democrats charge that the president abused his office by improperly leveraging U.S. foreign policy to try to dig up dirt on former Vice President Joe Biden and his son Hunter Biden and to pursue a debunked theory that Ukraine, not Russia, was behind the hacking of Democratic Party emails in 2016.

President Trump’s defenders insist that while the president may have asked the Ukrainian leader for help with certain matters, it was entirely appropriate and there was no quid pro quo. Acting White House Chief of Staff Mick Mulvaney recently complicated that argument by seeming to say there was a quid pro quo, but that’s a common feature of foreign policy – an assertion he later tried to walk back.

On Tuesday, explosive testimony from William Taylor Jr., the senior U.S. diplomat in Ukraine, added a new dimension and new urgency to the quid pro quo question. Mr. Taylor told House impeachment investigators that President Trump did withhold Ukraine aid and a promised White House meeting for Ukraine’s leader until Ukrainian officials publicly promised to investigate the Bidens, father and son.

If true Mr. Taylor’s assertions would directly contradict the president’s “no quid pro quo” stance, while calling into question the accuracy of several impeachment witnesses who have stated they were unaware of such pressure.

What did Mr. Taylor say?

Mr. Taylor was acting ambassador for the U.S. in Ukraine. His Tuesday testimony occurred behind closed doors, but news organizations obtained copies of his 15-page opening statement, which was apparently based on copious notes and memos for the record from Mr. Taylor’s files.

In short, he said that the quid pro quo was real, and drew a line directly from President Trump to the mysterious withholding of American military aid intended to help Ukraine defend against Russian incursion on its territory.

“I said on September 9 in a message to [Ambassador to the European Union] Gordon Sondland that withholding security assistance in exchange for help with a domestic political campaign in the United States would be ‘crazy’. I believed that then, and I still believe that,” Mr. Taylor said in his opening statement.

Mr. Taylor said that Mr. Sondland, a wealthy hotelier and political appointee who donated to the Trump campaign, informed him of the reasons for the unusual hold in a phone call. Everything was dependent on a public statement by Ukraine of an investigation into Biden-related matters, Mr. Sondland said, according to Mr. Taylor.

The president wanted Ukraine in a “public box,” Mr. Taylor was told. Presumably this would help ensure the investigations really occurred. It might also have been a means, by itself, of throwing doubt on the honesty of former Vice President Biden and his son.

“Ambassador Sondland tried to explain to me that President Trump is a businessman,” Mr. Taylor said in his statement. “When a businessman is about to sign a check to someone who owes him something, he said, the businessman asks that person to pay up before signing the check.”

A diplomat with five decades of experience, Mr. Taylor described a situation in which there were two channels for Ukraine policy, “one regular, and one highly irregular.” The latter consisted of Mr. Sondland, special envoy to Ukraine Kurt Volker, Energy Secretary Rick Perry, and the president’s lawyer Rudy Giuliani.

What happens now?

Democrats who heard Mr. Taylor’s testimony described it as a possible inflection point in their impeachment inquiry. Republicans were tight-lipped about what the diplomat had said.

There is sure to be a fight over Mr. Taylor’s credibility, and over the question of whether his statements really describe a direct line from the Oval Office to Ukraine, or simply his mistaken impression of what the circumstances were in this case.

One possible line of defense: GOP lawmakers are likely to describe Mr. Taylor as a bureaucrat disgruntled by the fact that the Trump administration was sapping the bureaucracy’s power and implementing new policies on its own, of which the career State Department hierarchy simply disapproved.

Democratic House investigators are almost certain to try and speak again with Mr. Sondland. In his previous appearance, compelled by a House subpoena, Mr. Sondland had said that President Trump had told him there was no quid pro quo in this instance, but he was not certain of the truth of that assertion. He also said that he did not recall having discussions with any State Department or White House official about former Vice President Biden or his son.

Would a quid pro quo be an impeachable offense?

It may all come down to Mr. Trump’s intent.

In many circumstances it is perfectly proper for a high U.S. official, even a president, to ask foreign countries for assistance with an ongoing law enforcement investigation, according to George Washington University law professor Jonathan Turley.

“Such calls can shortcut bureaucratic red tape, particularly if the evidence is held, as with this case, by national security or justice officials,” Mr. Turley wrote in an October 2 column in The Hill.

It may also be appropriate in some circumstances for a president to ask a foreign country to investigate a political rival, as President Trump appears to have done by urging the Ukrainian president to investigate the activities of former Vice President Biden and his son Hunter Biden. As Ohio State constitutional law professor Edward Foley points out in Politico, it all depends on what the rival may have been doing, and whether the president has the nation’s broader interests at heart.

In 1804, former Vice President Aaron Burr contacted the British government, looking for foreign support to cut the western portion of the U.S. away to form a separate country. President Thomas Jefferson, who detested Mr. Burr, eventually had the former vice president tried for treason. Probing this alleged deal was clearly in the country’s interest.

“Jefferson as president would have been acting responsibly if he had requested Britain’s assistance in the investigation of Burr,” Mr. Foley writes. 

In his dealings with Ukraine, including his call to investigate Mr. Biden and his son, was Mr. Trump acting for the good of the nation, or the benefit of himself? The impeachment inquiry will be tasked with answering that question. Evidence may include public statements and private discussions among staff members about possible quid pro quos.

To determine intent, lawmakers will have to judge what they believe was in Mr. Trump’s heart, as well as his actions.

“That is a tricky – but not impossible – bar for Congress to clear,” writes Mr. Foley.

Ari Jalal/Reuters

A convoy of U.S. vehicles is seen after withdrawing from northern Syria, on the outskirts of Dohuk, Iraq, October 21, 2019.

The upheaval and terrible violence in Syria are just one sign. The same thing is happening elsewhere: not only in the Middle East, but as far afield as Eastern Europe and East Asia.

We are seeing the beginnings of an answer to a question with potentially critical implications: What happens when a superpower decides it no longer wants to be a superpower?

The United States remains the world’s preeminent economic and military power. Only one other country, China, harbors realistic ambitions to displace it from that position. And the U.S. is not suddenly going to shrink into the geopolitical equivalent of Nepal, or Luxembourg, or Paraguay.

Yet its status as a superpower has been rooted in something more than mere economic or military muscle. It has rested on political and diplomatic leadership, and on a web of alliances around the world, formal and informal, that has magnified U.S. influence. The result: Even in areas of conflict where Washington has not directly sought to intervene, its mere presence has exercised a major influence. Its voice has mattered, and it has been listened to. 

That’s what is changing under President Donald Trump, with Syria providing the most dramatic evidence.

In Syria, it was Mr. Trump’s predecessor, Barack Obama, who decided against significant U.S. military involvement in the country’s civil war. But in his determination to roll back the so-called Islamic State, President Obama did draw on America’s superpower toolbox. The U.S. was critical in assembling an international partnership of more than 70 countries to take on the Islamic State group. And militarily, it forged a battlefield alliance with Kurdish fighters, backing them with money, weapons, training, and a small contingent of special-forces troops.

With ISIS beaten back, at least territorially, the situation in Syria until this month had settled into a delicate balance of power. The regime of President Bashar al-Assad, backed by Russian forces, was gradually moving to control more of the country. President Recep Tayyip Erdoğan of Turkey, to the north, continued his monthslong public insistence that northern Syria be cleared of the US-allied Kurds.

In pure military terms, there was little to stop Turkey: fewer than 2,000 U.S. soldiers on the ground. But for Mr. Erdoğan, and for Mr. Assad and Russian forces as well, it was not the troop numbers that forestalled any advance. It was the insignia on their uniforms: the potential price of taking on the whole range of measures available to the U.S. as a superpower. It was the U.S. presence that mattered.

Once the Trump administration signaled it no longer cared to remain, Mr. Erdoğan’s army, reportedly backed by jihadist irregulars, surged into Syria. Mr. Assad’s troops pushed northward as well into the roughly one-third of the country controlled by the U.S.-backed Kurds. And while what comes next is uncertain – Iran also has forces in Syria – one thing is clear: All diplomatic roads now lead through Russia, where Mr. Erdoğan has now traveled for talks with President Vladimir Putin. 

Washington’s fairly low-key response to last month’s Iranian attack on key Saudi oil facilities was seen in the region as conveying a similar message, prompting the Saudis to explore their own options for de-escalation with Tehran, and also to welcome Mr. Putin for talks.

But it’s not just in the Middle East that the absence – or at least the quieting – of America’s voice seems to be having an impact. In Asia, Japan and South Korea, two of Washington’s key allies, have been locked in a political battle, escalating into a trade war. At issue is a deeply felt enmity dating from Japan’s often-brutal colonial rule over the Korean Peninsula in the first half of the last century.

That’s not something any outside power can simply wish away. But the U.S. has, over decades, played a critical role in damping down such crises between allies. That’s now made more complicated by a similar retreat from engagement in Asia: first, at the start of the Trump administration, by withdrawing from the Trans-Pacific Partnership, an alliance set up with U.S. backing to balance the expanding influence of China; and more recently, by calling into question the value of continued U.S. troop deployments in South Korea.

In Europe, there’s similar concern over Mr. Trump’s questioning of the importance of the NATO military alliance, and of the implications that might have, for instance, in Ukraine, where Mr. Putin has annexed Crimea. At issue, as in Syria, is not whether there should be U.S. forces on the ground to forestall further advances there or elsewhere in Eastern Europe. It is the deterrent importance of America’s superpower commitment, its political and diplomatic presence, and its voice.

The longer-term question is whether there might be a return to American superpower engagement. Mr. Trump seems to enjoy broad support on at least one issue: That in the wake of the long and still-unresolved war in Iraq, the U.S. should steer clear of major military operations overseas. But the strong bipartisan criticism of his pullout from Syria, especially over the evident gains for Messrs. Erdoğan, Assad, and Putin, suggests that the effects of a more fundamental disengagement could be causing alarm.

President Donald Trump’s recasting of United States immigration policy isn’t just about letting fewer newcomers into the country. It’s also about redefining who is worthy to enter.

His administration’s stated criterion: those who are self-sufficient.

To the president’s supporters, it’s common sense. Favoring the skilled can boost the U.S. economy. And favoring the industrious will reduce a rising taxpayer tab for federal safety-net programs. Nations like Australia and Canada have already gone down this path toward a merit-based system for immigrant visas, they say.

“The president has made no secret of the fact that he believes the American immigration system, first and foremost, is set up to work for America. That means economically and for the people [already] here,” Ken Cuccinelli, the acting director of U.S. Citizenship and Immigration Services, told reporters Wednesday at a Monitor Breakfast.

It’s an objective that resonates with voters like Tammy Waddell, who has a horse farm about an hour’s drive north of the nation’s capital and who calls the nation’s current immigration situation “out of control.”

But this ideal of self-sufficiency might not be so simple to put into practice. For one thing, it’s not easy to draw bright lines between “desirable” and “undesirable” immigrants.

Mr. Trump’s policies are reducing the number of available workers in an already tight job market. Across America, many help-wanted ads are for low-skilled jobs, not for the college graduates favored by the president. A rule finalized recently by Mr. Cuccinelli could sharply limit the pool of immigrants available for low-wage work. It seeks to block green cards to people deemed likely to enroll in federal welfare programs. 

Matt Orlando/The Christian Science Monitor

Ken Cuccinelli, acting head of the agency that oversees legal immigration, has announced rules that would winnow out many green-card applicants based on their likelihood of drawing on federal support. Here he speaks at a breakfast hosted by The Christian Science Monitor in Washington on Oct. 16, 2019.

“It’s a very misleading definition of self-sufficiency,” says Elizabeth Lower-Basch, an expert on income and benefits at the Center for Law and Social Policy in Washington. “The vast majority of working-age adults who receive Medicaid [or food assistance] are in fact working.”

The ‘economic value’ of immigrants

The new restrictions, based on whether someone is likely to become a “public charge,” build on federal laws and guidelines going back as far as 1882. The Trump administration has created a more detailed and restrictive rule tied to U.S. law. Last week, judges in several federal courts blocked it from going into effect. 

Critics say the rule would amount to revising the land-of-opportunity ideal embodied at the base of the Statue of Liberty, where the famous words of poet Emma Lazarus say: “Give me your tired, your poor, your huddled masses yearning to breathe free.”

Backers of the policy, including Mr. Cuccinelli, defend a heightened focus on the “economic value” of immigrants. And he notes that the new criteria are aimed at family or employment immigrants, not those who seek access to the U.S. on a humanitarian basis as refugees or asylees.

“We continue to provide … the most long-term permanent relief in the world. So our position as the No. 1 most generous country in the world is not at any risk,” he asserted at the Monitor Breakfast. Still, Mr. Cuccinelli also discussed Trump administration plans to roll back the volume of entrants in those humanitarian categories.

What does the economy need?

Some economic-policy experts argue that curtailing the number of immigrants – and screening them in ways that narrow ethnic and socioeconomic diversity – could backfire economically. The current demand is for low-skill workers and the outsize contributions that immigrants make to the formation of new businesses.

“We have an economy that is full of jobs that fill vital needs but are not paying very well and often do not provide health insurance,” says Ms. Lower-Basch. “And so people get these supports from the government to supplement their work. Whereas ‘public charge’ was really written about people who ... were going to entirely rely on the government and not support themselves at all.”

Recent Trump actions seek to screen out applicants who can’t show they’ll be able to buy health insurance – putting up a major obstacle for many would-be immigrants.

Jonathan Ernst/Reuters

Immigrant-rights organizations, including CASA and the Service Employees International Union, rally at the Capitol in Washington Sept. 9, 2019, calling on Congress to create a path to permanent status for Temporary Protected Status holders and Deferred Action for Child Arrivals recipients.

That could be a problem for the economy, say some employers, who complain of a shortage of workers in general or who say not all skilled immigrants come with money and college degrees in hand. 

The U.S. Chamber of Commerce supports programs to attract both high- and low-skill immigrants. In a recent blog post it cited an “ominous” decline in the number of people coming from overseas to study at U.S. universities – often a path toward employment. “Concerns about our nation’s immigration system” were viewed by many as a key reason. 

Many economists say immigrants pay taxes that outweigh the public benefits they receive, contribute to innovation in ways that can be stunted by policies that restrict their diversity, and don’t erode opportunities for native-born residents.

Still, public opinion remains sharply divided, at a time when immigrants account for nearly 14% of the U.S. population, not far from prior-century peaks seen around 1910.

Maryland shows the variety views

In rural Frederick County, in Maryland, the county sheriff is seeking to collaborate with federal officials against unauthorized immigrants. Residents have formed opposing camps over whether the need is to combat racism and xenophobia or to uphold the rule of law.

To Ms. Wadell, the principle of self-sufficiency goes hand-in-hand with limiting immigration to those who apply and are accepted through legal channels.

“Be legal and work, and I don’t have a problem,” she says, as she and her husband fill their truck with gas before heading home to care for their horses. In her view, many immigrants rely on welfare programs at the expense of taxpayers.”

In the city of Frederick, not far from the Pennsylvania border, some see it differently.

“It’s a huge myth that immigrants are coming here to get public assistance,” says Michael Haverty, who works at a music and arts shop. “It’s also a big myth that … you stay on public assistance forever.” 

For him, a reference point is his own family heritage. “My ancestors came here in the 1840s from Ireland in our darkest chapter,” Mr. Haverty says. They worked their way from poverty into mainstream U.S. life, he says, as immigrants have been doing ever since. 

A few storefronts down, Jorge Ovando is adjusting an umbrella and cleaning a table outside a Peruvian restaurant. He is on a visa from Peru, aiming to earn money for a business degree and to polish his English language skills.

Mr. Ovando notes that his own job was created by a fellow Peruvian who started at a bottom-level restaurant job and worked his way up to a supervisory job and then opening this small cafe.

The question of self-sufficiency

But some experts say there’s good logic behind the Trump administration’s heightened focus on self-sufficiency.

“In welfare policy in general, one of the touchstones of the Trump administration has been to expect more individuals to work or participate in constructive activities,” says Matt Weidinger, a poverty expert at the American Enterprise Institute in Washington. 

The Trump administration’s attempted shift toward a more merit-based system “is not a question of who is intrinsically a better human being,” says Mark Krikorian, executive director of the Center for Immigration Studies, which advocates for less immigration. “We want immigrants that we expect to be able to thrive – and in a modern post-industrial knowledge-based economy, that means having a certain level of education and arriving with a certain knowledge of English.”

The Trump administration’s goal is not only to enforce the new criteria. It also wants to emphasize employment more (and family ties less) in selecting legal immigrants.

But one question is whether that overlooks the value of interdependence. In the current economy, many people contribute as workers even while receiving some public support.

For example, the public charge rule, if it passes muster in court, would mean that “legal immigrants with disabilities will be unable to apply for and receive needed services to find and maintain employment,” Stacy Cervenka of the American Foundation for the Blind wrote recently. She calls that “entirely contradictory to DHS’s professed intention to ensure that immigrants are self-sufficient.”

As divisive as the issues are, many on both sides of the political spectrum say America’s immigration challenges ultimately will require bipartisan legislative answers. Mr. Cuccinelli said “there’s only so much we’re going to do by regulation and rule without Congress’s participation.”

Mark Greenberg, an expert at the Migration Policy Institute, takes the point a step further. “There’s a strong argument,” he says in an email, “that if there’s going to be a major shift in policy about who gets admitted to the country, that decision ought to be made by Congress – not by giving immigration officials broad discretion to implement a complex test without safeguards to prevent arbitrariness.”

Staff writer Sarah Matusek contributed to this report from Boston.

Editor's note: One sentence has been updated to remove a reference to the coming vacancy in the role of acting secretary of Homeland Security. 

If you can’t beat them, eat them. That is the common wisdom of many scientists, conservationists, and fishermen who dream of ridding the western Atlantic of invasive lionfish, a stunning aquarium fish that, when introduced in the wild, dominates and destroys reef ecosystems. However, catching lionfish has never been simple; they are not easily targeted by line or net fishing. Now, a surprising new invention may bring lionfish hunting to the masses and help clear the seas of this invader: a submersible robot.

With its striking stripes, diaphanous fins, and mane of colorful but poisonous spines, the exotic Indo-Pacific lionfish makes for a popular aquarium fish. But when released into the Atlantic in the 1980s (presumably by aquarium aficionados who tired of the voracious pet), the fish thrived and became a menace to native fish species and the reefs they rely upon. Lionfish populations first exploded off Florida’s coast; now, lionfish have expanded their range throughout the Bahamas and the Caribbean all the way down to South America. 

“A number of characteristics make the lionfish the perfect invader,” says Stephen Gittings, a coral reef ecologist and NOAA’s chief scientist for the National Marine Sanctuary System. “They can eat fish up to half their body size and a single lionfish can eat dozens of fish in a day. Since no native species prey on lionfish, you’re not losing very many of them over the course of time so they just dominate and take over.”   

What’s more, a single female lionfish can lay up to 2 million eggs a year, which are impervious to predation since they are housed in an inedible sac. Once lionfish are established in an area it is very difficult to get rid of them and they can quickly destroy much of a reef’s biodiversity. Lionfish can strip a reef of 90% of its juvenile fish species in as little as five weeks.

Reef Roomba to the rescue  

Colin Angle, the co-founder of iRobot, which produces the automated vacuum known as the Roomba, is an avid diver. When diving in the Bahamas a few years ago, Mr. Angle spotted a beautiful fish wreathed in a mane of colorful spines. He took pictures of the fish, which he showed the dive boat’s captain. The captain took one look at the photo and spit over the side of the boat in a show of disgust. It was, of course, a lionfish. 

Determined to use his access to technology to tackle the lionfish problem, Mr. Angle directed his nonprofit, Robots in Service of the Environment (RSE), to develop a submersible robot that could descend to great depths to gather lionfish. From this, the Guardian was born.  

The Guardian is a 20-pound submersible remotely operated vehicle equipped with cameras and lights – and two paddles that can deliver a 20-volt shock to a lionfish. In a boat above, a human driver with a laptop guides the Guardian toward lionfish, and can push a button that activates the paddles to stun the fish. Once stunned, they are vacuumed into a water-filled storage chamber that can hold up to 20 fish. When the chamber is filled, the Guardian returns to the surface with its catch. 

“We’re providing the low-cost scalable robot that can hunt and capture lionfish and effectively bring the ability to hunt lionfish to anyone,” says Adam Cantor, director of engineering at RSE. “We provide the hardware and software needed to capture these fish to local everyday fishermen and tourists at a reasonable cost. People can have some fun and at the same time protect the reef.”

Lionfish. It’s what’s for dinner.  

Lionfish aren’t just pretty – they happen to make a tasty and nutritious meal. A spearfishing diver can bag a dozen or more lionfish in a day and sell the catch to local restaurants or retailers such as Whole Foods. Many coastal communities now hold derbies that pull in thousands of lionfish over the course of a few days.

“The issue is that lionfish can be found all the way down to a thousand feet and they breed between 200 and 400 feet deep and aggregate there. There’s no diving you can do to reach that depth,” says Mr. Cantor. “So that’s where we come in. As you go deeper, it’s much more cost-effective to use the robot. Also, by catching lionfish where they are breeding and hibernating you make sure that they never make it to the shallow reefs and therefore can’t devastate those native populations.”  

The Guardian is currently priced at $1,000, and RSE plans to put it on the market next year. Lionfish sell for over $5 a pound and a single machine can catch up to 20 fish per dive. 

“I think absolutely there’s a market for it. There’s a ton of lionfish down deeper that we can’t get to,” says Andy Lowe, a professional diver and lionfish hunter. “The thousand-dollar price point is very good, but for me to personally consider buying one I’ll need to see it get a lionfish off a reef at depth. If it can do that it’s got great potential.”

How many people purchase the Guardian to hunt lionfish remains to be seen, and without consumer buy-in, the impact of the Guardian will be limited. RSE plans to expand the scope of the Guardian’s work to include other underwater jobs like inspecting pipelines and the hulls of ships or conducting underwater surveys. It views the Guardian as the first of many future projects.

“In the background, we are looking at other environmental issues that robots could help resolve,” says Andrew Doucette, communications lead at RSE. “There are several invasive species around the world that we think robots could help with like pythons in Florida or the urchins in California but we might not always be underwater. We could end up doing something in the Sahara Desert, I don’t know.”

Reuters

Pipelines run at the McKay River Suncor oil sands operations near Fort McMurray, Alberta.

In many Western democracies, the politics of climate change is opening old fractures that require as much attention as climate change. In France, for example, rural folks dependent on cars for a living rioted last year over a government hike in gas prices, forcing President Emmanuel Macron to retreat and then revamp how he governs. Now it is Canada’s turn to deal with its own rupture over carbon issues.

After an election on Monday, Prime Minister Justin Trudeau faces a possible rebellion in two big energy-rich provinces, Alberta and Saskatchewan, which contain the world’s third-largest proven reserves of oil. Mr. Trudeau’s Liberal Party won the election but lost its majority in the House of Commons. It also lost big in the western Canada. The results mean the Liberals will be forced into alliances with smaller – and greener – parties eager to prevent the export of oil from the two provinces.

Until now, Mr. Trudeau has tried to balance Canada’s interest in being a leader on climate change with its vast oil wealth. In a grand political bargain last year, he was able to impose a national carbon tax while at the same time promising to rescue a proposed project to expand an oil pipeline from Alberta to the Pacific coast.

Now that pipeline may not be built as a result of the election, raising talk in Alberta of splitting the province from Canada. The country’s old east-west divide has been revived, requiring the young prime minister to heal this national breach before it grows. One solution lies in helping Alberta better use its oil revenues to diversify its economy – as Norway has done with its petroleum wealth – lessening the need to extract oil for global markets. Expanding a pipeline may then become unnecessary.

Weaning Canada off fossil fuels will take political patience and a renewed interest in harmony among its provinces. Climate change is urgent, but not as urgent as Canada keeping its unity in order to deal with climate change.