Tres Hermanos

And more?

The more refers to Diamond Bar's sphere of influence south of the city.

Cities in Los Angeles County are allowed to specify the potential use of unincorprated areas within their sphere of influence for later annexation.

Diamond Bar's southern sphere of influence is a wild, undeveloped part of the Missing Middle wildlife corridor. (See the map below)

We want Diamond Bar's General Plan to ensure this undeveloped area becomes permanant wild open space.

That plan is being developed now. The time to get involved is now.


Diamond Bar General Plan update data appears to assist developers in mowing down our precious Oaks

By under-reporting our sensitive habit on official documents, Diamond Bar, in effect, appears to claim no sensitive habitat. exists in our city.

On the contrary, Diamond Bar is one of the most biologically and ecologically sensitive cities in the entire country. Read more.

Please get involved to help us stop this travesty.

City of Industry proposes 2000 acres of solar panels in Tres Hermanos

Despite claiming that no such plans existed, the City of Industry has been working quietly and out of public view on a multimillion-dollar proposal to build a massive solar farm amid more than 2,000 acres of undeveloped rolling hills of Tres Hermanos Ranch. Read More

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Help us save Tres Hermanos

City of Industry is now negotiating behind closed doors to develop the rolling hills between Diamond Bar and Chino Hills. Read More.

Tres Hermanos from Grand Ave

Why this crown jewel must be saved

Natural open space is Diamond Bar's and Chino Hills' most precious asset.

•    Natural open land is a proven way of storing and reducing carbon emissions in forests, grasslands and wetlands through natural climate solutions.

•    Tres Hermanos Ranch is part of the last remaining large, unprotected tracts of open space left within the Puente-Chino Hills Wildlife Corridor. Its preservation is critical to the ecological sustainability of the region.

•    Tres Hermanos Ranch is in one of the most biodiverse, ecologically sensitive hotspots in the entire world. Yes, really. In the entire world. Hotspot defined. See map.

•    These 2450 acres are a diverse habitat wetland, which already provides temperature regulation, cleaner air, water filtration, and emotional relief for all of us.

•    Known as the "Missing Middle," this sprawling property abuts Tonner Canyon, forming a large, unprotected region that provides habitat for many threatened and endangered species.

Tres Hermanos Google map.

Our Vision

Preserve Tres Hermanos Ranch entirely as a nature reserve or state park.

•    Diamond Bar and Chino Hills will reap cultural and economic benefits as gateway cities to a unique Southern California ecotourism destination.

•    We see eco-education opportunities, limited recreation (walking, hiking, equestrian, bike trails); carefully planned active sport fields.

Backed up freeway traffic.

Why our vision matters:

The fate of Tres Hermanos Ranch and Diamond Bar's Sphere of Influence is being decided now!

•    Commercial or residential use of this area would make our horrible area traffic even worse, decreasing our quality of life. No feasible way exists to mitigate the additional traffic.

•    If this wildland is fragmented by development, Nature's solutions will be gone forever.

•    We, as citizens, must pressure our city decision makers to secure it as a natural living legacy for future generations.

•    We, as citizens, must make sure that Diamond Bar's conservation element in the General Plan update, designates Diamond Bar's Sphere of Influence and Tres Hermanos Ranch as natural open space.

Tres Hermanos Google map.

Tres Hermanos Ranch with Wildlife seen in and around it.

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