At the start of singer-songwriter Joni Mitchell’s first trip to Hawaii, more than four decades ago, she threw back hotel curtains and gazed at beautiful green mountains in the distance. Then, she recalled in a Los Angeles Times account, “I looked down and there was a parking lot as far as the eye could see, and it broke my heart … this blight on paradise. That’s when I sat down and wrote the song,” which includes the lament: Don’t it always seem to go that you don’t know what you’ve got till it’s gone.

Those lyrics, popularized in the 1970 tune “Big Yellow Taxi,” hold cautionary-tale relevance today as the city’s still-malleable transit-oriented development (TOD) directives are attracting developers, including one that already wants to push past building-height rules for a proposed high-rise mauka of Ala Moana Center, near the 20-mile rail line’s envisioned last stop.

ProsPac — headed by a founding shareholder of Shanghai HuaRui bank, the first private bank in Shanghai — wants to build a 400-unit condo mauka of Walgreens on the corner of Makaloa and Keeaumoku streets. The high-rise would be 400 feet tall. Existing zoning for the site allows buildings up to 250 feet, but under TOD rules — tailored with incentives for development — the maximum height is 350 feet. ProsPac may seek a variance for extra density, too.

In return for variances, the developer is promising a public-benefits package that includes open space of about 9,000 square feet around the building and another 5,500 square feet in an arcade with 28-foot ceilings. Plus, there would be more than the minimum amount of affordable housing required by the city, although Pros-Pac has not specified how much.

Approval of height and density proposals that exceed standard zoning is up to the City Council. Before taking action on any variance request tied to a TOD project, city leaders must take a hard look at what we’ve got — before it’s gone.

The TOD framers maintain that what we’ve got is opportunity to build 21 rail stations —from East Kapolei to Ala Moana Center— surrounded by “diverse, walkable neighborhoods,” with each station area establishing a “sense of place by celebrating historic and cultural assets; connecting homes with employment and education centers; and providing convenient access to goods, services, and recreation.”

More than any other rail station along the line, the Ala Moana Center terminus is expected to bump up area property values and tax revenues, according to the Ala Moana Neighborhood TOD’s draft final plan, which pledges to “guide development in such a manner that optimizes value capture while ensuring community benefits.”

Its rules for high-rise construction aim to balance residential and commercial concerns. If the City Council wants to grant a variance to accommodate ProsPac or any other developer, it must drive a hard bargain, befitting the city’s position in the catbird seat.

The Ala Moana Center station is projected to be the largest boarding station along the rail line, with more than 22,000 daily boardings expected. On behalf of future generations, the public today must consider whether to allow that hub to be edged by a crowded concrete-and-glass high-rise corridor.

In addition to ProsPac’s yet-to-be-named high-rise, plans are in the works for at least five others nearby. And in neighboring Kakaako, where a couple of rail stations also are planned, special state development rules apply and already allow 400-foot-tall buildings — the tallest in the state.

Some sections of the Ala Moana neighborhood now serve as lingering reminders that Hawaii has indeed paved some choice bits of paradise and put up plenty of parking lots. The neighborhood’s TOD plan describes its densely populated commercial stretches as lacking in character and “formless,” and notes a need for more greenery — community parks and recreational facilities — as well as safe pathways for pedestrians and cyclists.

Now is the time, as the vision for transit-oriented development continues to take shape, to take stock of what we’ve got.